test: add main test cases

Author: mohammadumar-dev

main_test.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestSemanticSummaryIncludesSymbolsFromLargeNewFile(t *testing.T) {
+	var diff strings.Builder
+	diff.WriteString("diff --git a/main.go b/main.go\n")
+	diff.WriteString("new file mode 100644\n")
+	diff.WriteString("--- /dev/null\n")
+	diff.WriteString("+++ b/main.go\n")
+	diff.WriteString("@@ -0,0 +1,220 @@\n")
+	diff.WriteString("+package main\n")
+	for i := 0; i < 120; i++ {
+		diff.WriteString("+// filler line\n")
+	}
+	diff.WriteString("+func generateUsefulCommitMessage() string {\n")
+	diff.WriteString("+\treturn \"ok\"\n")
+	diff.WriteString("+}\n")
+
+	change := FileChange{FileName: "main.go", Status: "??", Diff: diff.String()}
+	context := buildFileChangeContext(change, 1200)
+
+	if !strings.Contains(context, "Change type: new file") {
+		t.Fatalf("expected new file context, got:\n%s", context)
+	}
+	if !strings.Contains(context, "func generateUsefulCommitMessage") {
+		t.Fatalf("expected semantic symbol from large new file, got:\n%s", context)
+	}
+}
+
+func TestCommitMessageValidationRejectsNullAndGenericSubjects(t *testing.T) {
+	invalid := []string{
+		"feat: null handle",
+		"fix: update files",
+		"docs: changes",
+		"add useful context",
+	}
+	for _, message := range invalid {
+		if isUsableCommitMessage(message) {
+			t.Fatalf("expected %q to be rejected", message)
+		}
+	}
+
+	if !isUsableCommitMessage("feat: add semantic diff summaries") {
+		t.Fatal("expected specific conventional subject to be accepted")
+	}
+}
+
+func TestFallbackCommitMessageUsesAreaPrefix(t *testing.T) {
+	change := FileChange{
+		FileName: "README.md",
+		Status:   "M",
+		Diff:     "diff --git a/README.md b/README.md\n@@ -1 +1 @@\n-old\n+new\n",
+	}
+
+	message := fallbackCommitMessage([]FileChange{change})
+	if !strings.HasPrefix(message, "docs:") {
+		t.Fatalf("expected docs fallback prefix, got %q", message)
+	}
+}