diff --git a/lld/MachO/Driver.cpp b/lld/MachO/Driver.cpp
--- a/lld/MachO/Driver.cpp
+++ b/lld/MachO/Driver.cpp
@@ -338,14 +338,6 @@
   if (!orderFile.empty())
     parseOrderFile(orderFile);
 
-  // dyld requires us to load libSystem. Since we may run tests on non-OSX
-  // systems which do not have libSystem, we mock it out here.
-  // TODO: Replace this with a stub tbd file once we have TAPI support.
-  if (StringRef(getenv("LLD_IN_TEST")) == "1" &&
-      config->outputType == MH_EXECUTE) {
-    inputFiles.push_back(DylibFile::createLibSystemMock());
-  }
-
   if (config->outputType == MH_EXECUTE && !isa<Defined>(config->entry)) {
     error("undefined symbol: " + config->entry->getName());
     return false;
diff --git a/lld/MachO/InputFiles.h b/lld/MachO/InputFiles.h
--- a/lld/MachO/InputFiles.h
+++ b/lld/MachO/InputFiles.h
@@ -89,11 +89,6 @@
 
   static bool classof(const InputFile *f) { return f->kind() == DylibKind; }
 
-  // Do not use this constructor!! This is meant only for createLibSystemMock(),
-  // but it cannot be made private as we call it via make().
-  DylibFile();
-  static DylibFile *createLibSystemMock();
-
   StringRef dylibName;
   uint64_t ordinal = 0; // Ordinal numbering starts from 1, so 0 is a sentinel
   bool reexport = false;
diff --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp
--- a/lld/MachO/InputFiles.cpp
+++ b/lld/MachO/InputFiles.cpp
@@ -397,16 +397,6 @@
     reexported.push_back(make<DylibFile>(document, umbrella));
 }
 
-DylibFile::DylibFile() : InputFile(DylibKind, MemoryBufferRef()) {}
-
-DylibFile *DylibFile::createLibSystemMock() {
-  auto *file = make<DylibFile>();
-  file->mb = MemoryBufferRef("", "/usr/lib/libSystem.B.dylib");
-  file->dylibName = "/usr/lib/libSystem.B.dylib";
-  file->symbols.push_back(symtab->addDylib("dyld_stub_binder", file));
-  return file;
-}
-
 ArchiveFile::ArchiveFile(std::unique_ptr<llvm::object::Archive> &&f)
     : InputFile(ArchiveKind, f->getMemoryBufferRef()), file(std::move(f)) {
   for (const object::Archive::Symbol &sym : file->symbols())
diff --git a/lld/test/MachO/link-search-order.s b/lld/test/MachO/link-search-order.s
--- a/lld/test/MachO/link-search-order.s
+++ b/lld/test/MachO/link-search-order.s
@@ -10,7 +10,7 @@
 # RUN: llvm-ar --format=darwin crs %t/libgoodbye.a %t/goodbye.o
 #
 # RUN: llvm-mc -filetype obj -triple x86_64-apple-darwin %s -o %t/test.o
-# RUN: lld -flavor darwinnew -arch x86_64 -o %t/test -Z -L%t -lhello -lgoodbye %t/test.o
+# RUN: lld -flavor darwinnew -arch x86_64 -L%S/Inputs/MacOSX.sdk/usr/lib -o %t/test -Z -L%t -lhello -lgoodbye -lSystem %t/test.o
 #
 # RUN: llvm-objdump --macho --dylibs-used %t/test | FileCheck %s
 
diff --git a/lld/test/MachO/symbol-order.s b/lld/test/MachO/symbol-order.s
--- a/lld/test/MachO/symbol-order.s
+++ b/lld/test/MachO/symbol-order.s
@@ -5,7 +5,7 @@
 # RUN: echo ".global f; .section __TEXT,test_f2; f: ret"                | llvm-mc -filetype=obj -triple=x86_64-apple-darwin -o %t/f2.o
 # RUN: echo ".global f, g; .section __TEXT,test_fg; f: ret; g: callq f" | llvm-mc -filetype=obj -triple=x86_64-apple-darwin -o %t/fg.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t/test.o
-# RUN: lld -flavor darwinnew -arch x86_64 -dylib -o %t/libf1.dylib %t/f1.o
+# RUN: lld -flavor darwinnew -arch x86_64 -L%S/MacOSX.sdk/usr/lib -dylib -o %t/libf1.dylib %t/f1.o -lSystem
 
 # RUN: rm -f %t/libf2_g.a
 # RUN: llvm-ar rcs %t/libf2_g.a %t/f2.o %t/g.o
@@ -13,7 +13,7 @@
 # RUN: rm -f %t/libfg.a
 # RUN: llvm-ar rcs %t/libfg.a %t/fg.o
 
-# RUN: lld -flavor darwinnew -arch x86_64 %t/libf1.dylib %t/libf2_g.a %t/test.o -o %t/test.out
+# RUN: lld -flavor darwinnew -arch x86_64 -L%S/Inputs/MacOSX.sdk/usr/lib %t/libf1.dylib %t/libf2_g.a %t/test.o -o %t/test.out -lSystem
 # RUN: llvm-objdump --syms --macho --lazy-bind %t/test.out | FileCheck %s --check-prefix DYLIB-FIRST
 # DYLIB-FIRST:      SYMBOL TABLE:
 # DYLIB-FIRST-DAG:  __TEXT,test_g g
@@ -21,7 +21,7 @@
 # DYLIB-FIRST-NEXT: segment  section            address       dylib            symbol
 # DYLIB-FIRST-NEXT: __DATA   __la_symbol_ptr    {{[0-9a-z]+}} libf1            f
 
-# RUN: lld -flavor darwinnew -arch x86_64 %t/libf2_g.a %t/libf1.dylib %t/test.o -o %t/test.out
+# RUN: lld -flavor darwinnew -arch x86_64 -L%S/Inputs/MacOSX.sdk/usr/lib %t/libf2_g.a %t/libf1.dylib %t/test.o -o %t/test.out -lSystem
 # RUN: llvm-objdump --syms --macho --lazy-bind %t/test.out | FileCheck %s --check-prefix ARCHIVE-FIRST
 # ARCHIVE-FIRST:      SYMBOL TABLE:
 # ARCHIVE-FIRST-DAG:  __TEXT,test_f2 f
@@ -30,7 +30,7 @@
 # ARCHIVE-FIRST-NEXT: segment  section            address       dylib            symbol
 # ARCHIVE-FIRST-EMPTY:
 
-# RUN: lld -flavor darwinnew -arch x86_64 %t/libf1.dylib %t/libfg.a %t/test.o -o %t/test.out
+# RUN: lld -flavor darwinnew -arch x86_64 -L%S/Inputs/MacOSX.sdk/usr/lib %t/libf1.dylib %t/libfg.a %t/test.o -o %t/test.out -lSystem
 # RUN: llvm-objdump --syms --macho --lazy-bind %t/test.out | FileCheck %s --check-prefix ARCHIVE-PRIORITY
 # ARCHIVE-PRIORITY:      SYMBOL TABLE:
 # ARCHIVE-PRIORITY-DAG:  __TEXT,test_fg f