diff --git a/tools/aapt2/test/Common.cpp b/tools/aapt2/test/Common.cpp
index cdf24534..c7dd4c9 100644
--- a/tools/aapt2/test/Common.cpp
+++ b/tools/aapt2/test/Common.cpp
@@ -21,23 +21,6 @@
 namespace aapt {
 namespace test {
 
-struct TestDiagnosticsImpl : public android::IDiagnostics {
-  void Log(Level level, android::DiagMessageActual& actual_msg) override {
-    switch (level) {
-      case Level::Note:
-        return;
-
-      case Level::Warn:
-        std::cerr << actual_msg.source << ": warn: " << actual_msg.message << "." << std::endl;
-        break;
-
-      case Level::Error:
-        std::cerr << actual_msg.source << ": error: " << actual_msg.message << "." << std::endl;
-        break;
-    }
-  }
-};
-
 android::IDiagnostics* GetDiagnostics() {
   static TestDiagnosticsImpl diag;
   return &diag;
diff --git a/tools/aapt2/test/Common.h b/tools/aapt2/test/Common.h
index 0437980..b06c432 100644
--- a/tools/aapt2/test/Common.h
+++ b/tools/aapt2/test/Common.h
@@ -37,6 +37,32 @@
 namespace aapt {
 namespace test {
 
+struct TestDiagnosticsImpl : public android::IDiagnostics {
+  void Log(Level level, android::DiagMessageActual& actual_msg) override {
+    switch (level) {
+      case Level::Note:
+        return;
+
+      case Level::Warn:
+        std::cerr << actual_msg.source << ": warn: " << actual_msg.message << "." << std::endl;
+        log << actual_msg.source << ": warn: " << actual_msg.message << "." << std::endl;
+        break;
+
+      case Level::Error:
+        std::cerr << actual_msg.source << ": error: " << actual_msg.message << "." << std::endl;
+        log << actual_msg.source << ": error: " << actual_msg.message << "." << std::endl;
+        break;
+    }
+  }
+
+  std::string GetLog() {
+    return log.str();
+  }
+
+ private:
+  std::ostringstream log;
+};
+
 android::IDiagnostics* GetDiagnostics();
 
 inline ResourceName ParseNameOrDie(android::StringPiece str) {
diff --git a/tools/aapt2/test/Fixture.cpp b/tools/aapt2/test/Fixture.cpp
index b91abe5..570bcf1 100644
--- a/tools/aapt2/test/Fixture.cpp
+++ b/tools/aapt2/test/Fixture.cpp
@@ -91,10 +91,13 @@
 }
 
 bool CommandTestFixture::CompileFile(const std::string& path, const std::string& contents,
-                                     android::StringPiece out_dir, android::IDiagnostics* diag) {
+                                     android::StringPiece out_dir, android::IDiagnostics* diag,
+                                     const std::vector<android::StringPiece>& additional_args) {
   WriteFile(path, contents);
   CHECK(file::mkdirs(out_dir.data()));
-  return CompileCommand(diag).Execute({path, "-o", out_dir, "-v"}, &std::cerr) == 0;
+  std::vector<android::StringPiece> args = {path, "-o", out_dir, "-v"};
+  args.insert(args.end(), additional_args.begin(), additional_args.end());
+  return CompileCommand(diag).Execute(args, &std::cerr) == 0;
 }
 
 bool CommandTestFixture::Link(const std::vector<std::string>& args, android::IDiagnostics* diag) {
diff --git a/tools/aapt2/test/Fixture.h b/tools/aapt2/test/Fixture.h
index 14298d16..178d011 100644
--- a/tools/aapt2/test/Fixture.h
+++ b/tools/aapt2/test/Fixture.h
@@ -73,7 +73,8 @@
   // Wries the contents of the file to the specified path. The file is compiled and the flattened
   // file is written to the out directory.
   bool CompileFile(const std::string& path, const std::string& contents,
-                   android::StringPiece flat_out_dir, android::IDiagnostics* diag);
+                   android::StringPiece flat_out_dir, android::IDiagnostics* diag,
+                   const std::vector<android::StringPiece>& additional_args = {});
 
   // Executes the link command with the specified arguments.
   bool Link(const std::vector<std::string>& args, android::IDiagnostics* diag);