ported SketchWithExternC from legacy into integration test

internal/integrationtest/compile_4/compile_test.go

@@ -108,6 +108,7 @@ func TestCompileOfProblematicSketches(t *testing.T) {
 		{"SketchLibraryProvidesAllIncludes", testBuilderSketchLibraryProvidesAllIncludes},
 		{"UserHardware", testBuilderWithUserHardware},
 		{"SketchWithEnumClass", testBuilderSketchWithEnumClass},
+		{"SketchWithExternC", testBuilderSketchWithExternC},
 	}.Run(t, env, cli)
 }
 
@@ -661,6 +662,21 @@ func testBuilderSketchWithEnumClass(t *testing.T, env *integrationtest.Environme
 	})
 }
 
+func testBuilderSketchWithExternC(t *testing.T, env *integrationtest.Environment, cli *integrationtest.ArduinoCLI) {
+	t.Run("Build", func(t *testing.T) {
+		// Build
+		_, err := tryBuild(t, env, cli, "arduino:avr:leonardo")
+		require.NoError(t, err)
+	})
+
+	t.Run("Preprocess", func(t *testing.T) {
+		// Preprocess
+		sketchPath, preprocessedSketch, err := tryPreprocess(t, env, cli, "arduino:avr:leonardo")
+		require.NoError(t, err)
+		comparePreprocessGoldenFile(t, sketchPath, preprocessedSketch)
+	})
+}
+
 type builderOutput struct {
 	CompilerOut   string `json:"compiler_out"`
 	CompilerErr   string `json:"compiler_err"`

internal/integrationtest/compile_4/testdata/SketchWithExternC/SketchWithExternC.preprocessed.txt

@@ -0,0 +1,20 @@
+#include <Arduino.h>
+#line 1 "{{QuoteCppString .sketchMainFile}}"
+#line 1 "{{QuoteCppString .sketchMainFile}}"
+void setup();
+#line 6 "{{QuoteCppString .sketchMainFile}}"
+void loop();
+#line 11 "{{QuoteCppString .sketchMainFile}}"
+ extern "C" void test();
+#line 1 "{{QuoteCppString .sketchMainFile}}"
+void setup() {
+  // put your setup code here, to run once:
+  test();
+}
+
+void loop() {
+  // put your main code here, to run repeatedly:
+
+}
+
+extern "C" void test() {}

legacy/builder/test/try_build_of_problematic_sketch_test.go

@@ -29,10 +29,6 @@ import (
 
 // TODO add them in the compile_4
 
-func TestTryBuild037(t *testing.T) {
-	tryBuild(t, paths.New("sketch_with_externC", "sketch_with_externC.ino"))
-}
-
 func TestTryBuild038(t *testing.T) {
 	tryBuild(t, paths.New("sketch_with_multiline_prototypes", "sketch_with_multiline_prototypes.ino"))
 }