diff --git a/flang/unittests/Optimizer/Builder/Runtime/RuntimeCallTestBase.h b/flang/unittests/Optimizer/Builder/Runtime/RuntimeCallTestBase.h
new file mode 100644
--- /dev/null
+++ b/flang/unittests/Optimizer/Builder/Runtime/RuntimeCallTestBase.h
@@ -0,0 +1,97 @@
+//===- RuntimeCalltestBase.cpp -- Base for runtime call generation tests --===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_OPTIMIZER_BUILDER_RUNTIME_RUNTIMECALLTESTBASE_H
+#define FORTRAN_OPTIMIZER_BUILDER_RUNTIME_RUNTIMECALLTESTBASE_H
+
+#include "gtest/gtest.h"
+#include "flang/Optimizer/Builder/FIRBuilder.h"
+#include "flang/Optimizer/Support/InitFIR.h"
+#include "flang/Optimizer/Support/KindMapping.h"
+
+struct RuntimeCallTest : public testing::Test {
+public:
+  void SetUp() override {
+    mlir::OpBuilder builder(&context);
+    auto loc = builder.getUnknownLoc();
+
+    // Set up a Module with a dummy function operation inside.
+    // Set the insertion point in the function entry block.
+    mlir::ModuleOp mod = builder.create<mlir::ModuleOp>(loc);
+    mlir::FuncOp func = mlir::FuncOp::create(
+        loc, "func1", builder.getFunctionType(llvm::None, llvm::None));
+    auto *entryBlock = func.addEntryBlock();
+    mod.push_back(mod);
+    builder.setInsertionPointToStart(entryBlock);
+
+    fir::support::loadDialects(context);
+    kindMap = std::make_unique<fir::KindMapping>(&context);
+    firBuilder = std::make_unique<fir::FirOpBuilder>(mod, *kindMap);
+
+    i8Ty = firBuilder->getI8Type();
+    i16Ty = firBuilder->getIntegerType(16);
+    i32Ty = firBuilder->getI32Type();
+    i64Ty = firBuilder->getI64Type();
+    i128Ty = firBuilder->getIntegerType(128);
+
+    f32Ty = firBuilder->getF32Type();
+    f64Ty = firBuilder->getF64Type();
+    f80Ty = firBuilder->getF80Type();
+    f128Ty = firBuilder->getF128Type();
+
+    c4Ty = fir::ComplexType::get(firBuilder->getContext(), 4);
+    c8Ty = fir::ComplexType::get(firBuilder->getContext(), 8);
+    c10Ty = fir::ComplexType::get(firBuilder->getContext(), 10);
+    c16Ty = fir::ComplexType::get(firBuilder->getContext(), 16);
+  }
+
+  mlir::MLIRContext context;
+  std::unique_ptr<fir::KindMapping> kindMap;
+  std::unique_ptr<fir::FirOpBuilder> firBuilder;
+
+  // Commonly used types
+  mlir::Type i8Ty;
+  mlir::Type i16Ty;
+  mlir::Type i32Ty;
+  mlir::Type i64Ty;
+  mlir::Type i128Ty;
+  mlir::Type f32Ty;
+  mlir::Type f64Ty;
+  mlir::Type f80Ty;
+  mlir::Type f128Ty;
+  mlir::Type c4Ty;
+  mlir::Type c8Ty;
+  mlir::Type c10Ty;
+  mlir::Type c16Ty;
+};
+
+static void checkCallOp(
+    mlir::Operation *op, llvm::StringRef fctName, unsigned nbArgs) {
+  EXPECT_TRUE(mlir::isa<fir::CallOp>(*op));
+  auto callOp = mlir::dyn_cast<fir::CallOp>(*op);
+  EXPECT_TRUE(callOp.callee().hasValue());
+  mlir::SymbolRefAttr callee = *callOp.callee();
+  EXPECT_EQ(fctName, callee.getRootReference().getValue());
+  // sourceFile and sourceLine are added arguments.
+  EXPECT_EQ(nbArgs + 2, callOp.args().size());
+}
+
+static void checkCallOpFromResultBox(
+    mlir::Value result, llvm::StringRef fctName, unsigned nbArgs) {
+  EXPECT_TRUE(result.hasOneUse());
+  auto &u = result.users_begin();
+  if (mlir::isa<fir::CallOp>(*u.getOwner())) {
+    checkCallOp(u.getOwner(), fctName, nbArgs);
+  } else {
+    auto convOp = mlir::dyn_cast<fir::ConvertOp>(*u.getOwner());
+    checkCallOpFromResultBox(convOp.getResult(), fctName, nbArgs);
+  }
+}
+}
+
+#endif // FORTRAN_OPTIMIZER_BUILDER_RUNTIME_RUNTIMECALLTESTBASE_H