1 files changed, 56 insertions, 0 deletions
diff --git a/internal/showcase/code_extractor_test.go b/internal/showcase/code_extractor_test.go
new file mode 100644
index 0000000..d091f66
--- /dev/null
+++ b/internal/showcase/code_extractor_test.go
@@ -0,0 +1,56 @@
+package showcase
+
+import "testing"
+
+func TestIsCommentLine(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		trimmed string
+		want    bool
+	}{
+		{name: "slash comment", trimmed: "// comment", want: true},
+		{name: "hash comment", trimmed: "# comment", want: true},
+		{name: "include directive", trimmed: "#include <stdio.h>", want: false},
+		{name: "define directive", trimmed: "#define FOO 1", want: false},
+		{name: "html comment", trimmed: "<!-- comment -->", want: true},
+		{name: "block comment inner line", trimmed: "* comment", want: true},
+		{name: "single asterisk", trimmed: "*", want: false},
+		{name: "code line", trimmed: "fmt.Println(\"ok\")", want: false},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			got := isCommentLine(tc.trimmed)
+			if got != tc.want {
+				t.Fatalf("isCommentLine(%q) = %v, want %v", tc.trimmed, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestStripComments_PreservesPreprocessorDirectives(t *testing.T) {
+	t.Parallel()
+
+	code := `#include <stdio.h>
+#define VALUE 1
+# this is a comment
+int main() {
+    return VALUE; // trailing comment
+}`
+
+	got := stripComments(code)
+	want := `#include <stdio.h>
+#define VALUE 1
+int main() {
+    return VALUE;
+}`
+
+	if got != want {
+		t.Fatalf("stripComments() = %q, want %q", got, want)
+	}
+}