[flang] Change existing runtime tests to use gtest

[ashermancinelli]

Summary

Updates the flang runtime unittests to use GTest. This patch should
likely not be accepted as-is, as there are temporarily two directories
for runtime tests such that new tests may be
written to use GTest without interfering with the old ones. Eventually,
old runtime tests directory should be removed.

The style guide indicates that exceptions should never be used,
however almost all of the the current runtime tests use exceptions.
This revision removes this need for exceptions.

I attempted to follow the style guide as closely as possible, however
some of the files flang/unittests/Runtime differ in style from other
unittest directories. In these cases, I leaned towards conforming with
the other existing unittests and not the precedent set by
flang/unittests/Runtime directory. For example, for file names I used
pascal case instead of kabob case, and test cases are in pascal case
instead of camel case.

Some tests require input and will likely not be able to remain in the
same directory as the other runtime tests since LLVM's CMake unittest
functions do not allow multiple targets in a directory (as discussed
on slack). Example is

This is my first revision, so please point out anything that doesn't
conform to best practices.

[ashermancinelli]

@awarzynski Looks like I mistakenly abandoned the last revision for this. Should I keep this one open or should we stick to the abandoned one since you've already added other reviewers to it?

[ashermancinelli]

In D97381#2584941, @ashermancinelli wrote:

@awarzynski Looks like I mistakenly abandoned the last revision for this. Should I keep this one open or should we stick to the abandoned one since you've already added other reviewers to it?

Discussion has continued on the old revision (D97349) and I will prepare a new patch for this in smaller chunks. Closing this thread.

flang/unittests/CMakeLists.txt

if(NOT ARG_SLOW_TEST)
     add_dependencies(FlangUnitTests ${test_name}${suffix})
   endif()
 endfunction()
 
 add_subdirectory(Optimizer)
 add_subdirectory(Decimal)
 add_subdirectory(Evaluate)
 add_subdirectory(Runtime)
+add_subdirectory(RuntimeGTest)
 
 if (FLANG_BUILD_NEW_DRIVER)
   add_subdirectory(Frontend)
 endif()

flang/unittests/Runtime/CMakeLists.txt

 else()
   llvm_map_components_to_libnames(llvm_libs Support)
 endif()
 target_link_libraries(RuntimeTesting
   FortranRuntime
   ${llvm_libs}
 )
 
-add_flang_nongtest_unittest(format
-  RuntimeTesting
-  FortranRuntime
-)
-
 add_flang_nongtest_unittest(hello
   RuntimeTesting
   FortranRuntime
 )
 
 # This test is not run by default as it requires input.
 add_executable(external-hello-world
   external-hello.cpp
 )
 
 target_link_libraries(external-hello-world
   FortranRuntime
 )
 
 add_flang_nongtest_unittest(external-io
   RuntimeTesting
   FortranRuntime
 )
 
-add_flang_nongtest_unittest(list-input
-  RuntimeTesting
-  FortranRuntime
-)
-
 add_flang_nongtest_unittest(character
   RuntimeTesting
   FortranRuntime
 )

flang/unittests/Runtime/list-input.cpp

-// Basic sanity tests for list-directed input
-
-#include "testing.h"
-#include "../../runtime/descriptor.h"
-#include "../../runtime/io-api.h"
-#include "../../runtime/io-error.h"
-#include <algorithm>
-#include <cstring>
-
-using namespace Fortran::runtime;
-using namespace Fortran::runtime::io;
-
-int main() {
-  StartTests();
-
-  char buffer[4][32];
-  int j{0};
-  for (const char *p : {"1 2 2*3  ,", ",6,,8,1*",
-           "2*'abcdefghijklmnopqrstuvwxyzABC", "DEFGHIJKLMNOPQRSTUVWXYZ'"}) {
-    SetCharacter(buffer[j++], sizeof buffer[0], p);
-  }
-  for (; j < 4; ++j) {
-    SetCharacter(buffer[j], sizeof buffer[0], "");
-  }
-
-  StaticDescriptor<1> staticDescriptor;
-  Descriptor &whole{staticDescriptor.descriptor()};
-  SubscriptValue extent[]{4};
-  whole.Establish(TypeCode{CFI_type_char}, sizeof buffer[0], &buffer, 1, extent,
-      CFI_attribute_pointer);
-  whole.Dump();
-  whole.Check();
-
-  try {
-    auto cookie{IONAME(BeginInternalArrayListInput)(whole)};
-    std::int64_t n[9]{-1, -2, -3, -4, 5, -6, 7, -8, 9};
-    std::int64_t want[9]{1, 2, 3, 3, 5, 6, 7, 8, 9};
-    for (j = 0; j < 9; ++j) {
-      IONAME(InputInteger)(cookie, n[j]);
-    }
-    char asc[2][54]{};
-    IONAME(InputAscii)(cookie, asc[0], sizeof asc[0] - 1);
-    IONAME(InputAscii)(cookie, asc[1], sizeof asc[1] - 1);
-    if (auto status{IONAME(EndIoStatement)(cookie)}) {
-      Fail() << "list-directed input failed, status "
-             << static_cast<int>(status) << '\n';
-    } else {
-      for (j = 0; j < 9; ++j) {
-        if (n[j] != want[j]) {
-          Fail() << "wanted n[" << j << "]==" << want[j] << ", got " << n[j]
-                 << '\n';
-        }
-      }
-      for (j = 0; j < 2; ++j) {
-        if (std::strcmp(asc[j],
-                "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ") != 0) {
-          Fail() << "wanted asc[" << j << "]=alphabets, got '" << asc[j]
-                 << "'\n";
-        }
-      }
-    }
-  } catch (const std::string &crash) {
-    Fail() << "crash: " << crash << '\n';
-  }
-
-  return EndTests();
-}

flang/unittests/RuntimeGTest/CMakeLists.txt

+add_flang_unittest(FlangRuntimeTests
+  CharacterTest.cpp
+  CMakeLists.txt
+  ExternalIOTest.cpp
+  FormatTest.cpp
+  HelloWorldOutputTest.cpp
+  ListInputTest.cpp
+  RuntimeTesting.cpp
+)
+
+target_link_libraries(FlangRuntimeTests
+  PRIVATE
+  FortranRuntime
+)

flang/unittests/RuntimeGTest/CharacterTest.cpp

+// Basic sanity tests of CHARACTER API; exhaustive testing will be done
+// in Fortran.
+
+#include "../../runtime/character.h"
+#include "RuntimeTesting.h"
+#include "gtest/gtest.h"
+#include <cstring>
+
+using namespace Fortran::runtime;
+
+static void AppendAndPad(std::size_t limit) {
+  char x[8];
+  std::size_t xLen{0};
+  std::memset(x, 0, sizeof x);
+  xLen = RTNAME(CharacterAppend1)(x, limit, xLen, "abc", 3);
+  xLen = RTNAME(CharacterAppend1)(x, limit, xLen, "DE", 2);
+  RTNAME(CharacterPad1)(x, limit, xLen);
+  ASSERT_LE(xLen, limit) << "xLen " << xLen << ">" << limit;
+  if (x[limit]) {
+    EXPECT_TRUE(false) << "x[" << limit << "]='" << x[limit] << "'\n";
+    x[limit] = '\0';
+  }
+  ASSERT_FALSE(std::memcmp(x, "abcDE   ", limit)) << "x = '" << x << "'";
+}
+
+static void TestCharCompare(const char *x, const char *y, std::size_t xBytes,
+    std::size_t yBytes, int expect) {
+  int cmp{RTNAME(CharacterCompareScalar1)(x, y, xBytes, yBytes)};
+  char buf[2][8];
+  std::memset(buf, 0, sizeof buf);
+  std::memcpy(buf[0], x, xBytes);
+  std::memcpy(buf[1], y, yBytes);
+  ASSERT_EQ(cmp, expect) << "compare '" << buf[0] << "'(" << xBytes
+    << ") to '" << buf[1] << "'(" << yBytes << "), got " << cmp
+    << ", should be " << expect << '\n';
+}
+
+static void Compare(const char *x, const char *y, std::size_t xBytes,
+    std::size_t yBytes, int expect) {
+  TestCharCompare(x, y, xBytes, yBytes, expect);
+  TestCharCompare(y, x, yBytes, xBytes, -expect);
+}
+
+TEST(CharacterTests, CompareCharacters) {
+  StartTests();
+  for (std::size_t j{0}; j < 8; ++j) {
+    AppendAndPad(j);
+  }
+  Compare("abc", "abc", 3, 3, 0);
+  Compare("abc", "def", 3, 3, -1);
+  Compare("ab ", "abc", 3, 2, 0);
+  Compare("abc", "abc", 2, 3, -1);
+  EndTests();
+}

flang/unittests/RuntimeGTest/ExternalIOTest.cpp

+// Sanity test for all external I/O modes
+
+#include "RuntimeTesting.h"
+#include "../../runtime/io-api.h"
+#include "../../runtime/main.h"
+#include "../../runtime/stop.h"
+#include "gtest/gtest.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cstring>
+
+using namespace Fortran::runtime::io;
+
+TEST(ExternalIOTests, DirectUnformatted) {
+  // OPEN(NEWUNIT=unit,ACCESS='DIRECT',ACTION='READWRITE',&
+  //   FORM='UNFORMATTED',RECL=8,STATUS='SCRATCH')
+  auto io{IONAME(BeginOpenNewUnit)(__FILE__, __LINE__)};
+  ASSERT_TRUE(IONAME(SetAccess)(io, "DIRECT", 6)) << "SetAccess(DIRECT)";
+  ASSERT_TRUE(IONAME(SetAction)(io, "READWRITE", 9)) << "SetAction(READWRITE)";
+  ASSERT_TRUE(IONAME(SetForm)(io, "UNFORMATTED", 11)) << "SetForm(UNFORMATTED)";
+
+  std::int64_t buffer;
+  static constexpr std::size_t recl{sizeof buffer};
+  ASSERT_TRUE(IONAME(SetRecl)(io, recl)) << "SetRecl()";
+  ASSERT_TRUE(IONAME(SetStatus)(io, "SCRATCH", 7)) << "SetStatus(SCRATCH)";
+
+  int unit{-1};
+  ASSERT_TRUE(IONAME(GetNewUnit)(io, unit)) << "GetNewUnit(): unit=" << unit;
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for OpenNewUnit";
+
+  static constexpr int records{10};
+  for (int j{1}; j <= records; ++j) {
+    // WRITE(UNIT=unit,REC=j) j
+    io = IONAME(BeginUnformattedOutput)(unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(SetRec)(io, j)) << "SetRec(" << j << ')';
+    buffer = j;
+    ASSERT_TRUE(IONAME(OutputUnformattedBlock)
+      (io, reinterpret_cast<const char *>(&buffer), recl, recl))
+      << "OutputUnformattedBlock()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for OutputUnformattedBlock";
+  }
+
+  for (int j{records}; j >= 1; --j) {
+    // READ(UNIT=unit,REC=j) n
+    io = IONAME(BeginUnformattedInput)(unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(SetRec)(io, j)) << "SetRec(" << j << ')';
+    ASSERT_TRUE(IONAME(InputUnformattedBlock)
+        (io, reinterpret_cast<char *>(&buffer), recl, recl))
+      << "InputUnformattedBlock()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+        << "EndIoStatement() for InputUnformattedBlock";
+    ASSERT_EQ(buffer, j) << "Read back " << buffer
+      << " from direct unformatted record " << j << ", expected " << j;
+  }
+
+  // CLOSE(UNIT=unit,STATUS='DELETE')
+  io = IONAME(BeginClose)(unit, __FILE__, __LINE__);
+  ASSERT_TRUE(IONAME(SetStatus)(io, "DELETE", 6)) << "SetStatus(DELETE)";
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for Close";
+}
+
+TEST(ExternalIOTests, DirectUnformattedSwapped) {
+  // OPEN(NEWUNIT=unit,ACCESS='DIRECT',ACTION='READWRITE',&
+  //   FORM='UNFORMATTED',RECL=8,STATUS='SCRATCH',CONVERT='NATIVE')
+  auto io{IONAME(BeginOpenNewUnit)(__FILE__, __LINE__)};
+  ASSERT_TRUE(IONAME(SetAccess)(io, "DIRECT", 6)) << "SetAccess(DIRECT)";
+  ASSERT_TRUE(IONAME(SetAction)(io, "READWRITE", 9)) << "SetAction(READWRITE)";
+  ASSERT_TRUE(IONAME(SetForm)(io, "UNFORMATTED", 11)) << "SetForm(UNFORMATTED)";
+  ASSERT_TRUE(IONAME(SetConvert)(io, "NATIVE", 6)) << "SetConvert(NATIVE)";
+
+  std::int64_t buffer;
+  static constexpr std::size_t recl{sizeof buffer};
+  ASSERT_TRUE(IONAME(SetRecl)(io, recl)) << "SetRecl()";
+  ASSERT_TRUE(IONAME(SetStatus)(io, "SCRATCH", 7)) << "SetStatus(SCRATCH)";
+  int unit{-1};
+  ASSERT_TRUE(IONAME(GetNewUnit)(io, unit)) << "GetNewUnit()" << "unit="
+    << unit;
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for OpenNewUnit";
+
+  static constexpr int records{10};
+  for (int j{1}; j <= records; ++j) {
+    // WRITE(UNIT=unit,REC=j) j
+    io = IONAME(BeginUnformattedOutput)(unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(SetRec)(io, j)) << "SetRec(" << j << ')';
+    buffer = j;
+    ASSERT_TRUE(IONAME(OutputUnformattedBlock)
+        (io, reinterpret_cast<const char *>(&buffer), recl, recl))
+      << "OutputUnformattedBlock()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+        << "EndIoStatement() for OutputUnformattedBlock";
+  }
+
+  // OPEN(UNIT=unit,STATUS='OLD',CONVERT='SWAP')
+  io = IONAME(BeginOpenUnit)(unit, __FILE__, __LINE__);
+  ASSERT_TRUE(IONAME(SetStatus)(io, "OLD", 3)) << "SetStatus(OLD)";
+  ASSERT_TRUE(IONAME(SetConvert)(io, "SWAP", 4)) << "SetConvert(SWAP)";
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for OpenUnit";
+
+  for (int j{records}; j >= 1; --j) {
+    // READ(UNIT=unit,REC=j) n
+    io = IONAME(BeginUnformattedInput)(unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(SetRec)(io, j)) << "SetRec(" << j << ')';
+    ASSERT_TRUE(IONAME(InputUnformattedBlock)
+        (io, reinterpret_cast<char *>(&buffer), recl, recl))
+      << "InputUnformattedBlock()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for InputUnformattedBlock";
+    ASSERT_EQ((buffer >> 56), j) << "Read back " << (buffer >> 56)
+      << " from direct unformatted record " << j << ", expected " << j;
+  }
+
+  // CLOSE(UNIT=unit,STATUS='DELETE')
+  io = IONAME(BeginClose)(unit, __FILE__, __LINE__);
+  ASSERT_TRUE(IONAME(SetStatus)(io, "DELETE", 6)) << "SetStatus(DELETE)";
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for Close";
+}
+
+void TestSequentialFixedUnformatted() {
+  // OPEN(NEWUNIT=unit,ACCESS='SEQUENTIAL',ACTION='READWRITE',&
+  //   FORM='UNFORMATTED',RECL=8,STATUS='SCRATCH')
+  auto io{IONAME(BeginOpenNewUnit)(__FILE__, __LINE__)};
+  ASSERT_TRUE(IONAME(SetAccess)(io, "SEQUENTIAL", 10))
+    << "SetAccess(SEQUENTIAL)";
+  ASSERT_TRUE(IONAME(SetAction)(io, "READWRITE", 9)) << "SetAction(READWRITE)";
+  ASSERT_TRUE(IONAME(SetForm)(io, "UNFORMATTED", 11)) << "SetForm(UNFORMATTED)";
+
+  std::int64_t buffer;
+  static constexpr std::size_t recl{sizeof buffer};
+  ASSERT_TRUE(IONAME(SetRecl)(io, recl)) << "SetRecl()";
+  ASSERT_TRUE(IONAME(SetStatus)(io, "SCRATCH", 7)) << "SetStatus(SCRATCH)";
+  int unit{-1};
+  ASSERT_TRUE(IONAME(GetNewUnit)(io, unit)) << "GetNewUnit()";
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for OpenNewUnit";
+
+  static const int records{10};
+  for (int j{1}; j <= records; ++j) {
+    // DO J=1,RECORDS; WRITE(UNIT=unit) j; END DO
+    io = IONAME(BeginUnformattedOutput)(unit, __FILE__, __LINE__);
+    buffer = j;
+    ASSERT_TRUE(IONAME(OutputUnformattedBlock)
+        (io, reinterpret_cast<const char *>(&buffer), recl, recl))
+      << "OutputUnformattedBlock()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for OutputUnformattedBlock";
+  }
+
+  // REWIND(UNIT=unit)
+  io = IONAME(BeginRewind)(unit, __FILE__, __LINE__);
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for Rewind";
+  for (int j{1}; j <= records; ++j) {
+    // DO J=1,RECORDS; READ(UNIT=unit) n; check n; END DO
+    io = IONAME(BeginUnformattedInput)(unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(InputUnformattedBlock)
+        (io, reinterpret_cast<char *>(&buffer), recl, recl))
+      << "InputUnformattedBlock()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+        << "EndIoStatement() for InputUnformattedBlock";
+    ASSERT_EQ(buffer, j) << "Read back " << buffer
+             << " from sequential fixed unformatted record " << j
+             << ", expected " << j;
+  }
+
+  for (int j{records}; j >= 1; --j) {
+    // BACKSPACE(UNIT=unit)
+    io = IONAME(BeginBackspace)(unit, __FILE__, __LINE__);
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+        << "EndIoStatement() for Backspace (before read)";
+    // READ(UNIT=unit) n
+    io = IONAME(BeginUnformattedInput)(unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(InputUnformattedBlock)
+        (io, reinterpret_cast<char *>(&buffer), recl, recl))
+      << "InputUnformattedBlock()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+        << "EndIoStatement() for InputUnformattedBlock";
+    ASSERT_EQ(buffer, j) << "Read back " << buffer
+             << " from sequential fixed unformatted record " << j
+             << " after backspacing, expected " << j;
+    // BACKSPACE(UNIT=unit)
+    io = IONAME(BeginBackspace)(unit, __FILE__, __LINE__);
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for Backspace (after read)";
+  }
+
+  // CLOSE(UNIT=unit,STATUS='DELETE')
+  io = IONAME(BeginClose)(unit, __FILE__, __LINE__);
+  ASSERT_TRUE(IONAME(SetStatus)(io, "DELETE", 6)) << "SetStatus(DELETE)";
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for Close";
+}
+
+
+TEST(ExternalIOTests, SequentialVariableUnformatted) {
+  // OPEN(NEWUNIT=unit,ACCESS='SEQUENTIAL',ACTION='READWRITE',&
+  //   FORM='UNFORMATTED',STATUS='SCRATCH')
+  auto io{IONAME(BeginOpenNewUnit)(__FILE__, __LINE__)};
+  ASSERT_TRUE(IONAME(SetAccess)(io, "SEQUENTIAL", 10)) << "SetAccess(SEQUENTIAL)";
+  ASSERT_TRUE(IONAME(SetAction)(io, "READWRITE", 9)) << "SetAction(READWRITE)";
+  ASSERT_TRUE(IONAME(SetForm)(io, "UNFORMATTED", 11)) << "SetForm(UNFORMATTED)";
+  ASSERT_TRUE(IONAME(SetStatus)(io, "SCRATCH", 7)) << "SetStatus(SCRATCH)";
+
+  int unit{-1};
+  ASSERT_TRUE(IONAME(GetNewUnit)(io, unit)) << "GetNewUnit() unit=" << unit;
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for OpenNewUnit";
+
+  static const int records{10};
+  std::int64_t buffer[records]; // INTEGER*8 :: BUFFER(0:9) = [(j,j=0,9)]
+  for (int j{0}; j < records; ++j) {
+    buffer[j] = j;
+  }
+  for (int j{1}; j <= records; ++j) {
+    // DO J=1,RECORDS; WRITE(UNIT=unit) BUFFER(0:j); END DO
+    io = IONAME(BeginUnformattedOutput)(unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(OutputUnformattedBlock)
+        (io, reinterpret_cast<const char *>(&buffer), j * sizeof *buffer,
+         sizeof *buffer))
+      << "OutputUnformattedBlock()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for OutputUnformattedBlock";
+  }
+
+  // REWIND(UNIT=unit)
+  io = IONAME(BeginRewind)(unit, __FILE__, __LINE__);
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for Rewind";
+  for (int j{1}; j <= records; ++j) {
+    // DO J=1,RECORDS; READ(UNIT=unit) n; check n; END DO
+    io = IONAME(BeginUnformattedInput)(unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(InputUnformattedBlock)
+        (io, reinterpret_cast<char *>(&buffer), j * sizeof *buffer,
+         sizeof *buffer)) << "InputUnformattedBlock()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for InputUnformattedBlock";
+    for (int k{0}; k < j; ++k) {
+      ASSERT_EQ(buffer[k], k)
+        << "Read back [" << k << "]=" << buffer[k]
+        << " from direct unformatted record " << j << ", expected " << k;
+    }
+  }
+
+  for (int j{records}; j >= 1; --j) {
+    // BACKSPACE(unit)
+    io = IONAME(BeginBackspace)(unit, __FILE__, __LINE__);
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for Backspace (before read)";
+    // READ(unit=unit) n; check
+    io = IONAME(BeginUnformattedInput)(unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(InputUnformattedBlock)
+        (io, reinterpret_cast<char *>(&buffer), j * sizeof *buffer,
+         sizeof *buffer)) << "InputUnformattedBlock()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for InputUnformattedBlock";
+    for (int k{0}; k < j; ++k) {
+      ASSERT_EQ(buffer[k], k)
+        << "Read back [" << k << "]=" << buffer[k]
+        << " from sequential variable unformatted record " << j
+        << ", expected " << k << '\n';
+    }
+    // BACKSPACE(unit)
+    io = IONAME(BeginBackspace)(unit, __FILE__, __LINE__);
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+        << "EndIoStatement() for Backspace (after read)";
+  }
+  // CLOSE(UNIT=unit,STATUS='DELETE')
+  io = IONAME(BeginClose)(unit, __FILE__, __LINE__);
+  ASSERT_TRUE(IONAME(SetStatus)(io, "DELETE", 6)) << "SetStatus(DELETE)";
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for Close";
+}
+
+TEST(ExternalIOTests, DirectFormatted) {
+  // OPEN(NEWUNIT=unit,ACCESS='DIRECT',ACTION='READWRITE',&
+  //   FORM='FORMATTED',RECL=8,STATUS='SCRATCH')
+  auto io{IONAME(BeginOpenNewUnit)(__FILE__, __LINE__)};
+  ASSERT_TRUE(IONAME(SetAccess)(io, "DIRECT", 6)) << "SetAccess(DIRECT)";
+  ASSERT_TRUE(IONAME(SetAction)(io, "READWRITE", 9)) << "SetAction(READWRITE)";
+  ASSERT_TRUE(IONAME(SetForm)(io, "FORMATTED", 9)) << "SetForm(FORMATTED)";
+
+  static constexpr std::size_t recl{8};
+  ASSERT_TRUE(IONAME(SetRecl)(io, recl)) << "SetRecl()";
+  ASSERT_TRUE(IONAME(SetStatus)(io, "SCRATCH", 7)) << "SetStatus(SCRATCH)";
+
+  int unit{-1};
+  ASSERT_TRUE(IONAME(GetNewUnit)(io, unit)) << "GetNewUnit() unit=" << unit;
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for OpenNewUnit";
+
+  static constexpr int records{10};
+  static const char fmt[]{"(I4)"};
+  for (int j{1}; j <= records; ++j) {
+    // WRITE(UNIT=unit,FMT=fmt,REC=j) j
+    io = IONAME(BeginExternalFormattedOutput)(
+        fmt, sizeof fmt - 1, unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(SetRec)(io, j)) << "SetRec(" << j << ')';
+    ASSERT_TRUE(IONAME(OutputInteger64)(io, j)) << "OutputInteger64()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk) << "EndIoStatement() for OutputInteger64";
+  }
+
+  for (int j{records}; j >= 1; --j) {
+    // READ(UNIT=unit,FMT=fmt,REC=j) n
+    io = IONAME(BeginExternalFormattedInput)(
+        fmt, sizeof fmt - 1, unit, __FILE__, __LINE__);
+    ASSERT_TRUE(IONAME(SetRec)(io, j)) << "SetRec(" << j << ')';
+    std::int64_t buffer;
+    ASSERT_TRUE(IONAME(InputInteger)(io, buffer)) << "InputInteger()";
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for InputInteger";
+    ASSERT_EQ(buffer, j) << "Read back " << buffer
+      << " from direct formatted record " << j << ", expected " << j;
+  }
+  // CLOSE(UNIT=unit,STATUS='DELETE')
+  io = IONAME(BeginClose)(unit, __FILE__, __LINE__);
+  ASSERT_TRUE(IONAME(SetStatus)(io, "DELETE", 6)) << "SetStatus(DELETE)";
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for Close";
+}
+
+TEST(ExternalIOTests, SequentialVariableFormatted) {
+  // OPEN(NEWUNIT=unit,ACCESS='SEQUENTIAL',ACTION='READWRITE',&
+  //   FORM='FORMATTED',STATUS='SCRATCH')
+  auto io{IONAME(BeginOpenNewUnit)(__FILE__, __LINE__)};
+  ASSERT_TRUE(IONAME(SetAccess)(io, "SEQUENTIAL", 10))
+    << "SetAccess(SEQUENTIAL)";
+  ASSERT_TRUE(IONAME(SetAction)(io, "READWRITE", 9)) << "SetAction(READWRITE)";
+  ASSERT_TRUE(IONAME(SetForm)(io, "FORMATTED", 9)) << "SetForm(FORMATTED)";
+  ASSERT_TRUE(IONAME(SetStatus)(io, "SCRATCH", 7)) << "SetStatus(SCRATCH)";
+
+  int unit{-1};
+  ASSERT_TRUE(IONAME(GetNewUnit)(io, unit)) << "GetNewUnit() unit=" << unit;
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for OpenNewUnit";
+  static const int records{10};
+  std::int64_t buffer[records]; // INTEGER*8 :: BUFFER(0:9) = [(j,j=0,9)]
+  for (int j{0}; j < records; ++j) {
+    buffer[j] = j;
+  }
+  char fmt[32];
+  for (int j{1}; j <= records; ++j) {
+    std::snprintf(fmt, sizeof fmt, "(%dI4)", j);
+    // DO J=1,RECORDS; WRITE(UNIT=unit,FMT=fmt) BUFFER(0:j); END DO
+    io = IONAME(BeginExternalFormattedOutput)(
+        fmt, std::strlen(fmt), unit, __FILE__, __LINE__);
+    for (int k{0}; k < j; ++k) {
+      ASSERT_TRUE(IONAME(OutputInteger64)(io, buffer[k]))
+        << "OutputInteger64()";
+    }
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for OutputInteger64";
+  }
+
+  // REWIND(UNIT=unit)
+  io = IONAME(BeginRewind)(unit, __FILE__, __LINE__);
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk) << "EndIoStatement() for Rewind";
+  for (int j{1}; j <= records; ++j) {
+    std::snprintf(fmt, sizeof fmt, "(%dI4)", j);
+    // DO J=1,RECORDS; READ(UNIT=unit,FMT=fmt) n; check n; END DO
+    io = IONAME(BeginExternalFormattedInput)(
+        fmt, std::strlen(fmt), unit, __FILE__, __LINE__);
+    std::int64_t check[records];
+    for (int k{0}; k < j; ++k) {
+      ASSERT_TRUE(IONAME(InputInteger)(io, check[k])) << "InputInteger()";
+    }
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for InputInteger";
+    for (int k{0}; k < j; ++k) {
+      ASSERT_EQ(buffer[k], check[k]) << "Read back [" << k << "]=" << check[k]
+        << " from sequential variable formatted record " << j << ", expected "
+        << buffer[k];
+    }
+  }
+
+  for (int j{records}; j >= 1; --j) {
+    // BACKSPACE(unit)
+    io = IONAME(BeginBackspace)(unit, __FILE__, __LINE__);
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for Backspace (before read)";
+    std::snprintf(fmt, sizeof fmt, "(%dI4)", j);
+    // READ(UNIT=unit,FMT=fmt) n; check
+    io = IONAME(BeginExternalFormattedInput)(
+        fmt, std::strlen(fmt), unit, __FILE__, __LINE__);
+    std::int64_t check[records];
+    for (int k{0}; k < j; ++k) {
+      ASSERT_TRUE(IONAME(InputInteger)(io, check[k])) << "InputInteger()";
+    }
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for InputInteger";
+    for (int k{0}; k < j; ++k) {
+      ASSERT_EQ(buffer[k], check[k]) << "Read back [" << k << "]=" << buffer[k]
+        << " from sequential variable formatted record " << j << ", expected "
+        << buffer[k];
+    }
+    // BACKSPACE(unit)
+    io = IONAME(BeginBackspace)(unit, __FILE__, __LINE__);
+    ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+      << "EndIoStatement() for Backspace (after read)";
+  }
+  // CLOSE(UNIT=unit,STATUS='DELETE')
+  io = IONAME(BeginClose)(unit, __FILE__, __LINE__);
+  ASSERT_TRUE(IONAME(SetStatus)(io, "DELETE", 6)) << "SetStatus(DELETE)";
+  ASSERT_EQ(IONAME(EndIoStatement)(io), IostatOk)
+    << "EndIoStatement() for Close";
+}
+
+TEST(ExternalIOTests, StreamUnformatted) {
+  // TODO
+}

flang/unittests/RuntimeGTest/FormatTest.cpp

 // Tests basic FORMAT string traversal
 
-#include "testing.h"
+#include "RuntimeTesting.h"
 #include "../runtime/format-implementation.h"
 #include "../runtime/io-error.h"
+#include "gtest/gtest.h"
+#include <tuple>
 #include <cstdarg>
 #include <cstring>
 #include <string>
 #include <vector>
 
 using namespace Fortran::runtime;
 using namespace Fortran::runtime::io;
 using namespace std::literals::string_literals;
 
 using Results = std::vector<std::string>;
 
 // A test harness context for testing FormatControl
 class TestFormatContext : public IoErrorHandler {
 public:
   using CharType = char;
   TestFormatContext() : IoErrorHandler{"format.cpp", 1} {}
   bool Emit(const char *, std::size_t);
   bool Emit(const char16_t *, std::size_t);
   bool Emit(const char32_t *, std::size_t);
   bool AdvanceRecord(int = 1);
   void HandleRelativePosition(std::int64_t);
   void HandleAbsolutePosition(std::int64_t);
   void Report(const DataEdit &);
   void Check(Results &);
+
   Results results;
   MutableModes &mutableModes() { return mutableModes_; }
 
 private:
   MutableModes mutableModes_;
 };
 
 bool TestFormatContext::Emit(const char *s, std::size_t len) {
void TestFormatContext::Report(const DataEdit &edit) {
   if (edit.expoDigits) {
     str += "E"s + std::to_string(*edit.expoDigits);
   }
   // modes?
   results.push_back(str);
 }
 
 void TestFormatContext::Check(Results &expect) {
-  if (expect != results) {
-    Fail() << "expected:";
-    for (const std::string &s : expect) {
-      llvm::errs() << ' ' << s;
-    }
-    llvm::errs() << "\ngot:";
-    for (const std::string &s : results) {
-      llvm::errs() << ' ' << s;
-    }
-    llvm::errs() << '\n';
+  std::stringstream message;
+  message << "expected:";
+    message << ' ' << s;
+  message << ", got:";
+    message << ' ' << s;
   }
+  EXPECT_EQ(expect, results) << message.str();
   expect.clear();
   results.clear();
 }
 
-static void Test(int n, const char *format, Results &&expect, int repeat = 1) {
+// Tuple of types over which the test cases are parameterized
+using Params = std::tuple<int, const char*, Results, int>;
+
+// Fixture which constructs needed components for each test, includeing a
+// TestFormatContext
+struct FormatTestsFixture : ::testing::TestWithParam<Params> {
+  virtual void SetUp() {
+    StartTests();
+    std::tie(n, format, expect, repeat) = GetParam();
+  }
+  virtual void TearDown() {
+    ASSERT_NO_CRASHES() << " In teardown of FormatTestsFixture " << __FILE__
+      << __LINE__;
+    EndTests();
+  }
+protected:
+  int n;
+  const char* format;
+  Results expect;
+  int repeat;
   TestFormatContext context;
-  FormatControl<TestFormatContext> control{
+};
+
+TEST_P(FormatTestsFixture, FormatStringTraversal) {
+  FormatControl<decltype(context)> control{
       context, format, std::strlen(format)};
-  try {
-    for (int j{0}; j < n; ++j) {
-      context.Report(control.GetNextDataEdit(context, repeat));
-    }
-    control.Finish(context);
-    if (int iostat{context.GetIoStat()}) {
-      context.Crash("GetIoStat() == %d", iostat);
-    }
-  } catch (const std::string &crash) {
-    context.results.push_back("Crash:"s + crash);
-  }
+
+    context.Report(/*edit=*/control.GetNextDataEdit(context, repeat));
+    ASSERT_NO_CRASHES() << __FILE__ << " " << __LINE__;
+
+  int iostat{context.GetIoStat()};
+  ASSERT_FALSE(iostat) << "GetIoStat() == " << iostat;
+
   context.Check(expect);
+  ASSERT_NO_CRASHES() << __FILE__ << " " << __LINE__;
 }
 
-int main() {
-  StartTests();
-  Test(1, "('PI=',F9.7)", Results{"'PI='", "F9.7"});
-  Test(1, "(3HPI=F9.7)", Results{"'PI='", "F9.7"});
-  Test(1, "(3HPI=/F9.7)", Results{"'PI='", "/", "F9.7"});
-  Test(2, "('PI=',F9.7)", Results{"'PI='", "F9.7", "/", "'PI='", "F9.7"});
-  Test(2, "(2('PI=',F9.7),'done')",
-      Results{"'PI='", "F9.7", "'PI='", "F9.7", "'done'"});
-  Test(2, "(3('PI=',F9.7,:),'tooFar')",
-      Results{"'PI='", "F9.7", "'PI='", "F9.7"});
-  Test(2, "(*('PI=',F9.7,:),'tooFar')",
-      Results{"'PI='", "F9.7", "'PI='", "F9.7"});
-  Test(1, "(3F9.7)", Results{"2*F9.7"}, 2);
-  return EndTests();
-}
+// Trailing ',' in this macro suppresses a warning which is emmitted even when 
+// the macro is used correctly
+INSTANTIATE_TEST_CASE_P(FormatTests, FormatTestsFixture,
+    ::testing::Values(
+      std::make_tuple(1, "('PI=',F9.7)", Results{"'PI='", "F9.7"}, 1)
+      , std::make_tuple(1, "(3HPI=F9.7)", Results{"'PI='", "F9.7"}, 1)
+      , std::make_tuple(1, "(3HPI=/F9.7)", Results{"'PI='", "/", "F9.7"}, 1)
+      , std::make_tuple(2, "('PI=',F9.7)", Results{
+        "'PI='", "F9.7", "/", "'PI='", "F9.7"}, 1)
+      , std::make_tuple(2, "(2('PI=',F9.7),'done')", Results{
+        "'PI='", "F9.7", "'PI='", "F9.7", "'done'"}, 1)
+      , std::make_tuple(2, "(3('PI=',F9.7,:),'tooFar')", Results{
+        "'PI='", "F9.7", "'PI='", "F9.7"}, 1)
+      , std::make_tuple(2, "(*('PI=',F9.7,:),'tooFar')", Results{
+        "'PI='", "F9.7", "'PI='", "F9.7"}, 1)
+      , std::make_tuple(1, "(3F9.7)", Results{"2*F9.7"}, 2)
+      ),);

flang/unittests/RuntimeGTest/HelloWorldOutputTest.cpp

+// Basic sanity tests of I/O API; exhaustive testing will be done in Fortran
+
+#include "RuntimeTesting.h"
+#include "../../runtime/descriptor.h"
+#include "../../runtime/io-api.h"
+#include <cstring>
+#include <array>
+#include <tuple>
+
+using namespace Fortran::runtime;
+using namespace Fortran::runtime::io;
+
+static void VerifyFormat(const char *format, const char *expect, std::string &&got) {
+  std::string want{expect};
+  want.resize(got.size(), ' ');
+  EXPECT_EQ(want, got) << '\'' << format << "' failed. got '" << got
+    << "', expected '" << want << "'. " << want.size() << ' ' << got.size()
+    << ' ' << std::string(expect).size();
+}
+
+static void VerifyRealFormat(const char* format, double x, const char* expect) {
+  char buffer[800];
+  auto cookie{IONAME(BeginInternalFormattedOutput)(
+      buffer, sizeof buffer, format, std::strlen(format))};
+  IONAME(OutputReal64)(cookie, x);
+  auto status{IONAME(EndIoStatement)(cookie)};
+  ASSERT_FALSE(status) << '\'' << format << "' failed, status "
+    << static_cast<int>(status);
+  VerifyFormat(format, expect, std::string{buffer, sizeof buffer});
+}
+
+static void VerifyRealInputFormat(
+    const char *format, const char *data, std::uint64_t want) {
+  auto cookie{IONAME(BeginInternalFormattedInput)(
+      data, std::strlen(data), format, std::strlen(format))};
+  union {
+    double x;
+    std::uint64_t raw;
+  } u;
+  u.raw = 0;
+  IONAME(EnableHandlers)(cookie, true, true, true, true, true);
+  IONAME(InputReal64)(cookie, u.x);
+  char iomsg[65];
+  iomsg[0] = '\0';
+  iomsg[sizeof iomsg - 1] = '\0';
+  IONAME(GetIoMsg)(cookie, iomsg, sizeof iomsg - 1);
+  auto status{IONAME(EndIoStatement)(cookie)};
+  ASSERT_FALSE(status) << '\'' << format << "' failed reading '" << data
+    << "', status " << static_cast<int>(status) << " iomsg '" << iomsg << "'";
+  ASSERT_EQ(u.raw, want) << '\'' << format << "' failed reading '" << data
+    << "', want 0x" << std::hex << want << ", got 0x" << u.raw;
+}
+
+TEST(IOApiTests, HelloWorldOutputTest) {
+  StartTests();
+  char buffer[32];
+  const char *format{"(6HHELLO,,A6,2X,I3,1X,'0x',Z8,1X,L1)"};
+  auto cookie{IONAME(BeginInternalFormattedOutput)(
+      buffer, sizeof buffer, format, std::strlen(format))};
+  IONAME(OutputAscii)(cookie, "WORLD", 5);
+  IONAME(OutputInteger64)(cookie, 678);
+  IONAME(OutputInteger64)(cookie, 0xfeedface);
+  IONAME(OutputLogical)(cookie, true);
+  auto status{IONAME(EndIoStatement)(cookie)};
+  ASSERT_FALSE(status) << "hello: '" << format << "' failed, status "
+           << static_cast<int>(status);
+  VerifyFormat(format, "HELLO, WORLD  678 0xFEEDFACE T",
+      std::string{buffer, sizeof buffer});
+  EndTests();
+}
+
+TEST(IOApiTests, MultilineOutputTest) {
+  StartTests();
+  char buffer[5][32];
+  StaticDescriptor<1> staticDescriptor[2];
+  Descriptor &whole{staticDescriptor[0].descriptor()};
+  SubscriptValue extent[]{5};
+  whole.Establish(TypeCode{CFI_type_char}, sizeof buffer[0], &buffer, 1, extent,
+      CFI_attribute_pointer);
+  whole.Dump();
+  whole.Check();
+  Descriptor &section{staticDescriptor[1].descriptor()};
+  SubscriptValue lowers[]{0}, uppers[]{4}, strides[]{1};
+  section.Establish(whole.type(), whole.ElementBytes(), nullptr, 1, extent,
+      CFI_attribute_pointer);
+
+  auto error{
+    CFI_section(&section.raw(), &whole.raw(), lowers, uppers, strides)};
+  ASSERT_FALSE(error) << "multiline: CFI_section failed: " << error;
+
+  section.Dump();
+  section.Check();
+  const char *format{
+      "('?abcde,',T1,'>',T9,A,TL12,A,TR25,'<'//G0,17X,'abcd',1(2I4))"};
+  auto cookie{IONAME(BeginInternalArrayFormattedOutput)(
+      section, format, std::strlen(format))};
+  IONAME(OutputAscii)(cookie, "WORLD", 5);
+  IONAME(OutputAscii)(cookie, "HELLO", 5);
+  IONAME(OutputInteger64)(cookie, 789);
+  for (int j{666}; j <= 999; j += 111) {
+    IONAME(OutputInteger64)(cookie, j);
+  }
+
+  auto status{IONAME(EndIoStatement)(cookie)};
+  ASSERT_FALSE(status) << "multiline: '" << format << "' failed, status "
+           << static_cast<int>(status);
+  VerifyFormat(format,
+      ">HELLO, WORLD                  <"
+      "                                "
+      "789                 abcd 666 777"
+      " 888 999                        "
+      "                                ",
+      std::string{buffer[0], sizeof buffer});
+  EndTests();
+}
+
+TEST(IOApiTests, ListInputTest) {
+  StartTests();
+  static const char input[]{",1*,(5.,6..)"};
+  auto cookie{IONAME(BeginInternalListInput)(input, sizeof input - 1)};
+  float z[6];
+  for (int j{0}; j < 6; ++j) {
+    z[j] = -(j + 1);
+  }
+  for (int j{0}; j < 6; j += 2) {
+    ASSERT_TRUE(IONAME(InputComplex32)(cookie, &z[j]))
+      << "InputComplex32 failed\n";
+  }
+
+  auto status{IONAME(EndIoStatement)(cookie)};
+  ASSERT_FALSE(status) << "Failed complex list-directed input, status "
+    << static_cast<int>(status);
+
+  char output[33];
+  output[32] = '\0';
+  cookie = IONAME(BeginInternalListOutput)(output, 32);
+  for (int j{0}; j < 6; j += 2) {
+    ASSERT_TRUE(IONAME(OutputComplex32)(cookie, z[j], z[j + 1]))
+      << "OutputComplex32 failed";
+  }
+
+  status = IONAME(EndIoStatement)(cookie);
+  static const char expect[33]{" (-1.,-2.) (-3.,-4.) (5.,6.)    "};
+  ASSERT_FALSE(status) << "Failed complex list-directed output, status "
+      << static_cast<int>(status);
+  ASSERT_EQ(std::strncmp(output, expect, 33), 0) 
+    << "Failed complex list-directed output, expected '" << expect
+    << "', but got '" << output << "'";
+  EndTests();
+}
+
+TEST(IOApiTests, DescriptorOutputTest) {
+  StartTests();
+  char buffer[9];
+  // Formatted
+  const char *format{"(2A4)"};
+  auto cookie{IONAME(BeginInternalFormattedOutput)(
+      buffer, sizeof buffer, format, std::strlen(format))};
+  StaticDescriptor<1> staticDescriptor;
+  Descriptor &desc{staticDescriptor.descriptor()};
+  SubscriptValue extent[]{2};
+  char data[2][4];
+  std::memcpy(data[0], "ABCD", 4);
+  std::memcpy(data[1], "EFGH", 4);
+  desc.Establish(TypeCode{CFI_type_char}, sizeof data[0], &data, 1, extent);
+  desc.Dump();
+  desc.Check();
+  IONAME(OutputDescriptor)(cookie, desc);
+
+  auto formatStatus{IONAME(EndIoStatement)(cookie)};
+  ASSERT_FALSE(formatStatus) << "descrOutputTest: '" << format << "' failed, status "
+    << static_cast<int>(formatStatus);
+  VerifyFormat("descrOutputTest(formatted)", "ABCDEFGH ",
+      std::string{buffer, sizeof buffer});
+
+  // List-directed
+  cookie = IONAME(BeginInternalListOutput)(buffer, sizeof buffer);
+  IONAME(OutputDescriptor)(cookie, desc);
+  auto listDirectedStatus{IONAME(EndIoStatement)(cookie)};
+  ASSERT_FALSE(listDirectedStatus) << "descrOutputTest: list-directed failed, status "
+    << static_cast<int>(listDirectedStatus);
+  VerifyFormat("descrOutputTest(list)", " ABCDEFGH",
+      std::string{buffer, sizeof buffer});
+  EndTests();
+}
+
+TEST(IOApiTests, FormatZeroes) {
+  StartTests();
+  static constexpr std::pair<const char*, const char*> zeroes[] {
+    {"(E32.17,';')", "         0.00000000000000000E+00;"},
+    {"(F32.17,';')", "             0.00000000000000000;"},
+    {"(G32.17,';')", "          0.0000000000000000    ;"},
+    {"(DC,E32.17,';')", "         0,00000000000000000E+00;"},
+    {"(DC,F32.17,';')", "             0,00000000000000000;"},
+    {"(DC,G32.17,';')", "          0,0000000000000000    ;"},
+    {"(D32.17,';')", "         0.00000000000000000D+00;"},
+    {"(E32.17E1,';')", "          0.00000000000000000E+0;"},
+    {"(G32.17E1,';')", "           0.0000000000000000   ;"},
+    {"(E32.17E0,';')", "          0.00000000000000000E+0;"},
+    {"(G32.17E0,';')", "          0.0000000000000000    ;"},
+    {"(1P,E32.17,';')", "         0.00000000000000000E+00;"},
+    {"(1PE32.17,';')", "         0.00000000000000000E+00;"}, // no comma
+    {"(1P,F32.17,';')", "             0.00000000000000000;"},
+    {"(1P,G32.17,';')", "          0.0000000000000000    ;"},
+    {"(2P,E32.17,';')", "         00.0000000000000000E+00;"},
+    {"(-1P,E32.17,';')", "         0.00000000000000000E+00;"},
+    {"(G0,';')", "0.;"},
+  };
+
+  for(auto const& [format, expect] : zeroes) {
+    VerifyRealFormat(format, 0.0, expect);
+  }
+  EndTests();
+}
+
+TEST(IOApiTests, FormatOnes) {
+  StartTests();
+  static constexpr std::pair<const char*, const char*> ones[] {
+    {"(E32.17,';')", "         0.10000000000000000E+01;"},
+    {"(F32.17,';')", "             1.00000000000000000;"},
+    {"(G32.17,';')", "          1.0000000000000000    ;"},
+    {"(E32.17E1,';')", "          0.10000000000000000E+1;"},
+    {"(G32.17E1,';')", "           1.0000000000000000   ;"},
+    {"(E32.17E0,';')", "          0.10000000000000000E+1;"},
+    {"(G32.17E0,';')", "          1.0000000000000000    ;"},
+    {"(E32.17E4,';')", "       0.10000000000000000E+0001;"},
+    {"(G32.17E4,';')", "        1.0000000000000000      ;"},
+    {"(1P,E32.17,';')", "         1.00000000000000000E+00;"},
+    {"(1PE32.17,';')", "         1.00000000000000000E+00;"}, // no comma
+    {"(1P,F32.17,';')", "            10.00000000000000000;"},
+    {"(1P,G32.17,';')", "          1.0000000000000000    ;"},
+    {"(ES32.17,';')", "         1.00000000000000000E+00;"},
+    {"(2P,E32.17,';')", "         10.0000000000000000E-01;"},
+    {"(2P,G32.17,';')", "          1.0000000000000000    ;"},
+    {"(-1P,E32.17,';')", "         0.01000000000000000E+02;"},
+    {"(-1P,G32.17,';')", "          1.0000000000000000    ;"},
+    {"(G0,';')", "1.;"},
+  };
+
+  for(auto const& [format, expect] : ones) {
+    VerifyRealFormat(format, 1.0, expect);
+  }
+  EndTests();
+}
+
+TEST(IOApiTests, FormatNegativeOnes) {
+  StartTests();
+  static constexpr std::tuple<const char*, const char*> negOnes[] {
+    {"(E32.17,';')", "        -0.10000000000000000E+01;"},
+    {"(F32.17,';')", "            -1.00000000000000000;"},
+    {"(G32.17,';')", "         -1.0000000000000000    ;"},
+    {"(G0,';')", "-1.;"},
+  };
+  for(auto const& [format, expect] : negOnes) {
+    VerifyRealFormat(format, -1.0, expect);
+  }
+  EndTests();
+}
+
+TEST(IOApiTests, FormatDoubleValues) {
+  StartTests();
+
+  volatile union {
+    double d;
+    std::uint64_t n;
+  } u;
+
+  u.n = 0x8000000000000000; // -0
+  VerifyRealFormat("(E9.1,';')", u.d, " -0.0E+00;");
+  VerifyRealFormat("(F4.0,';')", u.d, " -0.;");
+  VerifyRealFormat("(G8.0,';')", u.d, "-0.0E+00;");
+  VerifyRealFormat("(G8.1,';')", u.d, " -0.    ;");
+  VerifyRealFormat("(G0,';')", u.d, "-0.;");
+  VerifyRealFormat("(E9.1,';')", u.d, " -0.0E+00;");
+  u.n = 0x7ff0000000000000; // +Inf
+  VerifyRealFormat("(E9.1,';')", u.d, "      Inf;");
+  VerifyRealFormat("(F9.1,';')", u.d, "      Inf;");
+  VerifyRealFormat("(G9.1,';')", u.d, "      Inf;");
+  VerifyRealFormat("(SP,E9.1,';')", u.d, "     +Inf;");
+  VerifyRealFormat("(SP,F9.1,';')", u.d, "     +Inf;");
+  VerifyRealFormat("(SP,G9.1,';')", u.d, "     +Inf;");
+  VerifyRealFormat("(G0,';')", u.d, "Inf;");
+  u.n = 0xfff0000000000000; // -Inf
+  VerifyRealFormat("(E9.1,';')", u.d, "     -Inf;");
+  VerifyRealFormat("(F9.1,';')", u.d, "     -Inf;");
+  VerifyRealFormat("(G9.1,';')", u.d, "     -Inf;");
+  VerifyRealFormat("(G0,';')", u.d, "-Inf;");
+  u.n = 0x7ff0000000000001; // NaN
+  VerifyRealFormat("(E9.1,';')", u.d, "      NaN;");
+  VerifyRealFormat("(F9.1,';')", u.d, "      NaN;");
+  VerifyRealFormat("(G9.1,';')", u.d, "      NaN;");
+  VerifyRealFormat("(G0,';')", u.d, "NaN;");
+  u.n = 0xfff0000000000001; // NaN (sign irrelevant)
+  VerifyRealFormat("(E9.1,';')", u.d, "      NaN;");
+  VerifyRealFormat("(F9.1,';')", u.d, "      NaN;");
+  VerifyRealFormat("(G9.1,';')", u.d, "      NaN;");
+  VerifyRealFormat("(SP,E9.1,';')", u.d, "      NaN;");
+  VerifyRealFormat("(SP,F9.1,';')", u.d, "      NaN;");
+  VerifyRealFormat("(SP,G9.1,';')", u.d, "      NaN;");
+  VerifyRealFormat("(G0,';')", u.d, "NaN;");
+
+  u.n = 0x3fb999999999999a; // 0.1 rounded
+  VerifyRealFormat("(E62.55,';')", u.d,
+      " 0.1000000000000000055511151231257827021181583404541015625E+00;");
+  VerifyRealFormat("(E0.0,';')", u.d, "0.E+00;");
+  VerifyRealFormat("(E0.55,';')", u.d,
+      "0.1000000000000000055511151231257827021181583404541015625E+00;");
+  VerifyRealFormat("(E0,';')", u.d, ".1E+00;");
+  VerifyRealFormat("(F58.55,';')", u.d,
+      " 0.1000000000000000055511151231257827021181583404541015625;");
+  VerifyRealFormat("(F0.0,';')", u.d, "0.;");
+  VerifyRealFormat("(F0.55,';')", u.d,
+      ".1000000000000000055511151231257827021181583404541015625;");
+  VerifyRealFormat("(F0,';')", u.d, ".1;");
+  VerifyRealFormat("(G62.55,';')", u.d,
+      " 0.1000000000000000055511151231257827021181583404541015625    ;");
+  VerifyRealFormat("(G0.0,';')", u.d, "0.;");
+  VerifyRealFormat("(G0.55,';')", u.d,
+      ".1000000000000000055511151231257827021181583404541015625;");
+  VerifyRealFormat("(G0,';')", u.d, ".1;");
+
+  u.n = 0x3ff8000000000000; // 1.5
+  VerifyRealFormat("(E9.2,';')", u.d, " 0.15E+01;");
+  VerifyRealFormat("(F4.1,';')", u.d, " 1.5;");
+  VerifyRealFormat("(G7.1,';')", u.d, " 2.    ;");
+  VerifyRealFormat("(RN,E8.1,';')", u.d, " 0.2E+01;");
+  VerifyRealFormat("(RN,F3.0,';')", u.d, " 2.;");
+  VerifyRealFormat("(RN,G7.0,';')", u.d, " 0.E+01;");
+  VerifyRealFormat("(RN,G7.1,';')", u.d, " 2.    ;");
+  VerifyRealFormat("(RD,E8.1,';')", u.d, " 0.1E+01;");
+  VerifyRealFormat("(RD,F3.0,';')", u.d, " 1.;");
+  VerifyRealFormat("(RD,G7.0,';')", u.d, " 0.E+01;");
+  VerifyRealFormat("(RD,G7.1,';')", u.d, " 1.    ;");
+  VerifyRealFormat("(RU,E8.1,';')", u.d, " 0.2E+01;");
+  VerifyRealFormat("(RU,G7.0,';')", u.d, " 0.E+01;");
+  VerifyRealFormat("(RU,G7.1,';')", u.d, " 2.    ;");
+  VerifyRealFormat("(RZ,E8.1,';')", u.d, " 0.1E+01;");
+  VerifyRealFormat("(RZ,F3.0,';')", u.d, " 1.;");
+  VerifyRealFormat("(RZ,G7.0,';')", u.d, " 0.E+01;");
+  VerifyRealFormat("(RZ,G7.1,';')", u.d, " 1.    ;");
+  VerifyRealFormat("(RC,E8.1,';')", u.d, " 0.2E+01;");
+  VerifyRealFormat("(RC,F3.0,';')", u.d, " 2.;");
+  VerifyRealFormat("(RC,G7.0,';')", u.d, " 0.E+01;");
+  VerifyRealFormat("(RC,G7.1,';')", u.d, " 2.    ;");
+
+  // TODO continue F and G editing tests on these data
+
+  u.n = 0xbff8000000000000; // -1.5
+  VerifyRealFormat("(E9.2,';')", u.d, "-0.15E+01;");
+  VerifyRealFormat("(RN,E8.1,';')", u.d, "-0.2E+01;");
+  VerifyRealFormat("(RD,E8.1,';')", u.d, "-0.2E+01;");
+  VerifyRealFormat("(RU,E8.1,';')", u.d, "-0.1E+01;");
+  VerifyRealFormat("(RZ,E8.1,';')", u.d, "-0.1E+01;");
+  VerifyRealFormat("(RC,E8.1,';')", u.d, "-0.2E+01;");
+
+  u.n = 0x4004000000000000; // 2.5
+  VerifyRealFormat("(E9.2,';')", u.d, " 0.25E+01;");
+  VerifyRealFormat("(RN,E8.1,';')", u.d, " 0.2E+01;");
+  VerifyRealFormat("(RD,E8.1,';')", u.d, " 0.2E+01;");
+  VerifyRealFormat("(RU,E8.1,';')", u.d, " 0.3E+01;");
+  VerifyRealFormat("(RZ,E8.1,';')", u.d, " 0.2E+01;");
+  VerifyRealFormat("(RC,E8.1,';')", u.d, " 0.3E+01;");
+
+  u.n = 0xc004000000000000; // -2.5
+  VerifyRealFormat("(E9.2,';')", u.d, "-0.25E+01;");
+  VerifyRealFormat("(RN,E8.1,';')", u.d, "-0.2E+01;");
+  VerifyRealFormat("(RD,E8.1,';')", u.d, "-0.3E+01;");
+  VerifyRealFormat("(RU,E8.1,';')", u.d, "-0.2E+01;");
+  VerifyRealFormat("(RZ,E8.1,';')", u.d, "-0.2E+01;");
+  VerifyRealFormat("(RC,E8.1,';')", u.d, "-0.3E+01;");
+
+  u.n = 1; // least positive nonzero subnormal
+  VerifyRealFormat("(E32.17,';')", u.d, "         0.49406564584124654-323;");
+  VerifyRealFormat("(ES32.17,';')", u.d, "         4.94065645841246544-324;");
+  VerifyRealFormat("(EN32.17,';')", u.d, "         4.94065645841246544-324;");
+  VerifyRealFormat("(E759.752,';')", u.d,
+      " 0."
+      "494065645841246544176568792868221372365059802614324764425585682500675507"
+      "270208751865299836361635992379796564695445717730926656710355939796398774"
+      "796010781878126300713190311404527845817167848982103688718636056998730723"
+      "050006387409153564984387312473397273169615140031715385398074126238565591"
+      "171026658556686768187039560310624931945271591492455329305456544401127480"
+      "129709999541931989409080416563324524757147869014726780159355238611550134"
+      "803526493472019379026810710749170333222684475333572083243193609238289345"
+      "836806010601150616980975307834227731832924790498252473077637592724787465"
+      "608477820373446969953364701797267771758512566055119913150489110145103786"
+      "273816725095583738973359899366480994116420570263709027924276754456522908"
+      "75386825064197182655334472656250-323;");
+  VerifyRealFormat("(G0,';')", u.d, ".5-323;");
+  VerifyRealFormat("(E757.750,';')", u.d,
+      " 0."
+      "494065645841246544176568792868221372365059802614324764425585682500675507"
+      "270208751865299836361635992379796564695445717730926656710355939796398774"
+      "796010781878126300713190311404527845817167848982103688718636056998730723"
+      "050006387409153564984387312473397273169615140031715385398074126238565591"
+      "171026658556686768187039560310624931945271591492455329305456544401127480"
+      "129709999541931989409080416563324524757147869014726780159355238611550134"
+      "803526493472019379026810710749170333222684475333572083243193609238289345"
+      "836806010601150616980975307834227731832924790498252473077637592724787465"
+      "608477820373446969953364701797267771758512566055119913150489110145103786"
+      "273816725095583738973359899366480994116420570263709027924276754456522908"
+      "753868250641971826553344726562-323;");
+  VerifyRealFormat("(RN,E757.750,';')", u.d,
+      " 0."
+      "494065645841246544176568792868221372365059802614324764425585682500675507"
+      "270208751865299836361635992379796564695445717730926656710355939796398774"
+      "796010781878126300713190311404527845817167848982103688718636056998730723"
+      "050006387409153564984387312473397273169615140031715385398074126238565591"
+      "171026658556686768187039560310624931945271591492455329305456544401127480"
+      "129709999541931989409080416563324524757147869014726780159355238611550134"
+      "803526493472019379026810710749170333222684475333572083243193609238289345"
+      "836806010601150616980975307834227731832924790498252473077637592724787465"
+      "608477820373446969953364701797267771758512566055119913150489110145103786"
+      "273816725095583738973359899366480994116420570263709027924276754456522908"
+      "753868250641971826553344726562-323;");
+  VerifyRealFormat("(RD,E757.750,';')", u.d,
+      " 0."
+      "494065645841246544176568792868221372365059802614324764425585682500675507"
+      "270208751865299836361635992379796564695445717730926656710355939796398774"
+      "796010781878126300713190311404527845817167848982103688718636056998730723"
+      "050006387409153564984387312473397273169615140031715385398074126238565591"
+      "171026658556686768187039560310624931945271591492455329305456544401127480"
+      "129709999541931989409080416563324524757147869014726780159355238611550134"
+      "803526493472019379026810710749170333222684475333572083243193609238289345"
+      "836806010601150616980975307834227731832924790498252473077637592724787465"
+      "608477820373446969953364701797267771758512566055119913150489110145103786"
+      "273816725095583738973359899366480994116420570263709027924276754456522908"
+      "753868250641971826553344726562-323;");
+  VerifyRealFormat("(RU,E757.750,';')", u.d,
+      " 0."
+      "494065645841246544176568792868221372365059802614324764425585682500675507"
+      "270208751865299836361635992379796564695445717730926656710355939796398774"
+      "796010781878126300713190311404527845817167848982103688718636056998730723"
+      "050006387409153564984387312473397273169615140031715385398074126238565591"
+      "171026658556686768187039560310624931945271591492455329305456544401127480"
+      "129709999541931989409080416563324524757147869014726780159355238611550134"
+      "803526493472019379026810710749170333222684475333572083243193609238289345"
+      "836806010601150616980975307834227731832924790498252473077637592724787465"
+      "608477820373446969953364701797267771758512566055119913150489110145103786"
+      "273816725095583738973359899366480994116420570263709027924276754456522908"
+      "753868250641971826553344726563-323;");
+  VerifyRealFormat("(RC,E757.750,';')", u.d,
+      " 0."
+      "494065645841246544176568792868221372365059802614324764425585682500675507"
+      "270208751865299836361635992379796564695445717730926656710355939796398774"
+      "796010781878126300713190311404527845817167848982103688718636056998730723"
+      "050006387409153564984387312473397273169615140031715385398074126238565591"
+      "171026658556686768187039560310624931945271591492455329305456544401127480"
+      "129709999541931989409080416563324524757147869014726780159355238611550134"
+      "803526493472019379026810710749170333222684475333572083243193609238289345"
+      "836806010601150616980975307834227731832924790498252473077637592724787465"
+      "608477820373446969953364701797267771758512566055119913150489110145103786"
+      "273816725095583738973359899366480994116420570263709027924276754456522908"
+      "753868250641971826553344726563-323;");
+
+  u.n = 0x10000000000000; // least positive nonzero normal
+  VerifyRealFormat("(E723.716,';')", u.d,
+      " 0."
+      "222507385850720138309023271733240406421921598046233183055332741688720443"
+      "481391819585428315901251102056406733973103581100515243416155346010885601"
+      "238537771882113077799353200233047961014744258363607192156504694250373420"
+      "837525080665061665815894872049117996859163964850063590877011830487479978"
+      "088775374994945158045160505091539985658247081864511353793580499211598108"
+      "576605199243335211435239014879569960959128889160299264151106346631339366"
+      "347758651302937176204732563178148566435087212282863764204484681140761391"
+      "147706280168985324411002416144742161856716615054015428508471675290190316"
+      "132277889672970737312333408698898317506783884692609277397797285865965494"
+      "10913690954061364675687023986783152906809846172109246253967285156250-"
+      "307;");
+  VerifyRealFormat("(G0,';')", u.d, ".22250738585072014-307;");
+
+  u.n = 0x7fefffffffffffffuLL; // greatest finite
+  VerifyRealFormat("(E32.17,';')", u.d, "         0.17976931348623157+309;");
+  VerifyRealFormat("(E317.310,';')", u.d,
+      " 0."
+      "179769313486231570814527423731704356798070567525844996598917476803157260"
+      "780028538760589558632766878171540458953514382464234321326889464182768467"
+      "546703537516986049910576551282076245490090389328944075868508455133942304"
+      "583236903222948165808559332123348274797826204144723168738177180919299881"
+      "2504040261841248583680+309;");
+  VerifyRealFormat("(ES317.310,';')", u.d,
+      " 1."
+      "797693134862315708145274237317043567980705675258449965989174768031572607"
+      "800285387605895586327668781715404589535143824642343213268894641827684675"
+      "467035375169860499105765512820762454900903893289440758685084551339423045"
+      "832369032229481658085593321233482747978262041447231687381771809192998812"
+      "5040402618412485836800+308;");
+  VerifyRealFormat("(EN319.310,';')", u.d,
+      " 179."
+      "769313486231570814527423731704356798070567525844996598917476803157260780"
+      "028538760589558632766878171540458953514382464234321326889464182768467546"
+      "703537516986049910576551282076245490090389328944075868508455133942304583"
+      "236903222948165808559332123348274797826204144723168738177180919299881250"
+      "4040261841248583680000+306;");
+  VerifyRealFormat("(G0,';')", u.d, ".17976931348623157+309;");
+
+  VerifyRealFormat("(F5.3,';')", 25., "*****;");
+  VerifyRealFormat("(F5.3,';')", 2.5, "2.500;");
+  VerifyRealFormat("(F5.3,';')", 0.25, "0.250;");
+  VerifyRealFormat("(F5.3,';')", 0.025, "0.025;");
+  VerifyRealFormat("(F5.3,';')", 0.0025, "0.003;");
+  VerifyRealFormat("(F5.3,';')", 0.00025, "0.000;");
+  VerifyRealFormat("(F5.3,';')", 0.000025, "0.000;");
+  VerifyRealFormat("(F5.3,';')", -25., "*****;");
+  VerifyRealFormat("(F5.3,';')", -2.5, "*****;");
+  VerifyRealFormat("(F5.3,';')", -0.25, "-.250;");
+  VerifyRealFormat("(F5.3,';')", -0.025, "-.025;");
+  VerifyRealFormat("(F5.3,';')", -0.0025, "-.003;");
+  VerifyRealFormat("(F5.3,';')", -0.00025, "-.000;");
+  VerifyRealFormat("(F5.3,';')", -0.000025, "-.000;");
+  EndTests();
+}
+
+TEST(IOApiTests, FormatDoubleInputValues) {
+  StartTests();
+  VerifyRealInputFormat("(F18.0)", "                 0", 0x0);
+  VerifyRealInputFormat("(F18.0)", "                  ", 0x0);
+  VerifyRealInputFormat("(F18.0)", "                -0", 0x8000000000000000);
+  VerifyRealInputFormat("(F18.0)", "                01", 0x3ff0000000000000);
+  VerifyRealInputFormat("(F18.0)", "                 1", 0x3ff0000000000000);
+  VerifyRealInputFormat("(F18.0)", "              125.", 0x405f400000000000);
+  VerifyRealInputFormat("(F18.0)", "              12.5", 0x4029000000000000);
+  VerifyRealInputFormat("(F18.0)", "              1.25", 0x3ff4000000000000);
+  VerifyRealInputFormat("(F18.0)", "             01.25", 0x3ff4000000000000);
+  VerifyRealInputFormat("(F18.0)", "              .125", 0x3fc0000000000000);
+  VerifyRealInputFormat("(F18.0)", "             0.125", 0x3fc0000000000000);
+  VerifyRealInputFormat("(F18.0)", "             .0625", 0x3fb0000000000000);
+  VerifyRealInputFormat("(F18.0)", "            0.0625", 0x3fb0000000000000);
+  VerifyRealInputFormat("(F18.0)", "               125", 0x405f400000000000);
+  VerifyRealInputFormat("(F18.1)", "               125", 0x4029000000000000);
+  VerifyRealInputFormat("(F18.2)", "               125", 0x3ff4000000000000);
+  VerifyRealInputFormat("(F18.3)", "               125", 0x3fc0000000000000);
+  VerifyRealInputFormat(
+      "(-1P,F18.0)", "               125", 0x4093880000000000); // 1250
+  VerifyRealInputFormat("(1P,F18.0)", "               125", 0x4029000000000000); // 12.5
+  VerifyRealInputFormat("(BZ,F18.0)", "              125 ", 0x4093880000000000); // 1250
+  VerifyRealInputFormat("(BZ,F18.0)", "       125 . e +1 ", 0x42a6bcc41e900000); // 1.25e13
+  VerifyRealInputFormat("(DC,F18.0)", "              12,5", 0x4029000000000000);
+  EndTests();
+}

flang/unittests/RuntimeGTest/ListInputTest.cpp

+// Basic sanity tests for list-directed input
+
+#include "RuntimeTesting.h"
+#include "gtest/gtest.h"
+#include "../../runtime/descriptor.h"
+#include "../../runtime/io-api.h"
+#include "../../runtime/io-error.h"
+#include <algorithm>
+#include <cstring>
+
+using namespace Fortran::runtime;
+using namespace Fortran::runtime::io;
+
+TEST(InputTest, ListInput) {
+  StartTests();
+  char buffer[4][32];
+  int j{0};
+  for (const char *p : {"1 2 2*3  ,", ",6,,8,1*",
+           "2*'abcdefghijklmnopqrstuvwxyzABC", "DEFGHIJKLMNOPQRSTUVWXYZ'"}) {
+    SetCharacter(buffer[j++], sizeof buffer[0], p);
+  }
+  for (; j < 4; ++j) {
+    SetCharacter(buffer[j], sizeof buffer[0], "");
+  }
+
+  StaticDescriptor<1> staticDescriptor;
+  Descriptor &whole{staticDescriptor.descriptor()};
+  SubscriptValue extent[]{4};
+  whole.Establish(TypeCode{CFI_type_char}, sizeof buffer[0], &buffer, 1, extent,
+      CFI_attribute_pointer);
+  whole.Dump();
+  whole.Check();
+
+  auto cookie{IONAME(BeginInternalArrayListInput)(whole)};
+  std::int64_t n[9]{-1, -2, -3, -4, 5, -6, 7, -8, 9};
+  std::int64_t want[9]{1, 2, 3, 3, 5, 6, 7, 8, 9};
+  for (j = 0; j < 9; ++j) {
+    IONAME(InputInteger)(cookie, n[j]);
+  }
+
+  char asc[2][54]{};
+  IONAME(InputAscii)(cookie, asc[0], sizeof asc[0] - 1);
+  IONAME(InputAscii)(cookie, asc[1], sizeof asc[1] - 1);
+
+  auto status{IONAME(EndIoStatement)(cookie)};
+  ASSERT_FALSE((bool)status) << "list-directed input failed, status "
+    << static_cast<int>(status) << '\n';
+  ASSERT_NO_CRASHES() << __FILE__ << ' ' << __LINE__;
+
+  for (j = 0; j < 9; ++j) {
+    ASSERT_EQ(n[j], want[j]) << "wanted n[" << j << "]==" << want[j]
+      << ", got " << n[j] << '\n';
+  }
+  ASSERT_NO_CRASHES() << __FILE__ << ' ' << __LINE__;
+
+  for (j = 0; j < 2; ++j) {
+    ASSERT_EQ(std::strcmp(asc[j],
+          "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ "), 0)
+      << "wanted asc[" << j << "]=alphabets, got '" << asc[j] << "'\n";
+  }
+  ASSERT_NO_CRASHES() << __FILE__ << ' ' << __LINE__;
+  EndTests();
+}

flang/unittests/RuntimeGTest/RuntimeTesting.h

+#ifndef FORTRAN_TEST_RUNTIME_TESTING_H_
+#define FORTRAN_TEST_RUNTIME_TESTING_H_
+
+#include "gtest/gtest.h"
+#include <cstddef>
+
+// Number of runtime crashes discoverd by the crash handler registered in the
+// `StartTests` function below.
+int GetNumRuntimeCrashes();
+
+// Registers a callback in the fortran runtime to register errors in tests.
+// When `rethrow` is false, you must check for runtime crashes yourself.
+void StartTests();
+
+// Resets static variables that should not carry over between tests
+void EndTests();
+
+// Defines a CHARACTER object with padding when needed
+void SetCharacter(char *, std::size_t, const char *);
+
+// Convenience assertion to ensure no crashes from within the fortran runtime
+// have occured.
+#define ASSERT_NO_CRASHES() \
+  ASSERT_EQ(GetNumRuntimeCrashes(), 0) \
+      << "Encountered " << GetNumRuntimeCrashes() << " runtime crashes! "
+
+#endif // FORTRAN_TEST_RUNTIME_TESTING_H_

flang/unittests/RuntimeGTest/RuntimeTesting.cpp

+#include "RuntimeTesting.h"
+#include "../../runtime/terminator.h"
+#include <algorithm>
+#include <cstdarg>
+#include <cstdio>
+#include <cstring>
+#include <string>
+
+static int failures{0};
+
+static bool hasRunStartTests{false};
+
+// Override the Fortran runtime's Crash() for testing purposes
+static void CatchCrash(
+    const char *sourceFile, int sourceLine, const char *message, va_list &ap) {
+  char buffer[1000];
+  std::vsnprintf(buffer, sizeof buffer, message, ap);
+  va_end(ap);
+  llvm::errs() << (sourceFile ? sourceFile : "unknown source file") << '('
+               << sourceLine << "): CRASH: " << buffer << '\n';
+  failures++;
+}
+
+int GetNumRuntimeCrashes() {
+  return failures;
+}
+
+void StartTests() {
+  if (hasRunStartTests)
+    return;
+  Fortran::runtime::Terminator::RegisterCrashHandler(CatchCrash);
+  hasRunStartTests = true;
+}
+
+void EndTests() {
+  ASSERT_NO_CRASHES();
+  failures = 0;
+}
+
+void SetCharacter(char *to, std::size_t n, const char *from) {
+  auto len{std::strlen(from)};
+  std::memcpy(to, from, std::min(len, n));
+  if (len < n) {
+    std::memset(to + len, ' ', n - len);
+  }
+}