From 105a984f16fb8c8154b489f519196ae922e74956 Mon Sep 17 00:00:00 2001
From: Aram Zegerius <aram@zegeri.us>
Date: Thu, 1 Aug 2024 10:43:22 +0200
Subject: [PATCH] Add integration test (#65)

---
 integration_test.go | 188 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 188 insertions(+)
 create mode 100644 integration_test.go

diff --git a/integration_test.go b/integration_test.go
new file mode 100644
index 0000000..85105b2
--- /dev/null
+++ b/integration_test.go
@@ -0,0 +1,188 @@
+package main_test
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+	"text/template"
+
+	"github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/plumbing/object"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCOBIntegration(t *testing.T) {
+	tempDir, err := os.MkdirTemp("", "cob-integration-test")
+	if err != nil {
+		t.Fatalf("failed to create temporary directory: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Build cob in the temporary directory
+	cmd := exec.Command("go", "build", "-o", tempDir, ".")
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("failed to build cob: %v\nOutput: %s", err, output)
+	}
+
+	// Initialize git repository
+	err = initGitRepo(tempDir)
+	if err != nil {
+		t.Fatalf("failed to initialize git repository: %v", err)
+	}
+
+	// Create two mock benchmark files, the second one slower than the first
+	err = createMockBenchmarks(tempDir)
+	if err != nil {
+		t.Fatalf("failed to create mock benchmarks: %v", err)
+	}
+
+	// Run cob in the temporary directory
+	cmd = exec.Command(filepath.Join(tempDir, "cob"))
+	cmd.Dir = tempDir
+	output, err = cmd.CombinedOutput()
+
+	// Expect an error because the second benchmark is slower than the first
+	if err == nil {
+		t.Fatalf("expected an error, but got none")
+	}
+
+	assert.Contains(t, string(output), "Comparison")
+	assert.Contains(t, string(output), "BenchmarkFoo")
+	assert.Contains(t, string(output), "This commit makes benchmarks worse")
+}
+
+func initGitRepo(dir string) error {
+	r, err := git.PlainInit(dir, false)
+	if err != nil {
+		return fmt.Errorf("failed to initialize git repository: %w", err)
+	}
+
+	w, err := r.Worktree()
+	if err != nil {
+		return fmt.Errorf("failed to get worktree: %w", err)
+	}
+
+	err = os.WriteFile(filepath.Join(dir, "go.mod"), []byte("module test\n"), 0644)
+	if err != nil {
+		return fmt.Errorf("failed to create go.mod: %w", err)
+	}
+
+	_, err = w.Add(".")
+	if err != nil {
+		return fmt.Errorf("failed to add go.mod: %w", err)
+	}
+
+	_, err = w.Commit("Initial commit", &git.CommitOptions{
+		Author: &object.Signature{
+			Name:  "Test User",
+			Email: "test@example.com",
+		},
+	})
+	if err != nil {
+		return fmt.Errorf("failed to commit: %w", err)
+	}
+
+	return nil
+}
+
+func createMockBenchmarks(dir string) error {
+	r, err := git.PlainOpen(dir)
+	if err != nil {
+		return fmt.Errorf("failed to open git repository: %w", err)
+	}
+
+	w, err := r.Worktree()
+	if err != nil {
+		return fmt.Errorf("failed to get worktree: %w", err)
+	}
+
+	tmpl := `
+package benchmark
+
+import "testing"
+
+func BenchmarkFoo(b *testing.B) {
+    for i := 0; i < b.N; i++ {
+        foo({{.Iterations}})
+    }
+}
+
+func foo(n int) int {
+    sum := 0
+    for i := 0; i < n; i++ {
+        sum += i
+    }
+    return sum
+}
+`
+
+	// Create initial (good) benchmark
+	if err := createBenchmarkFile(dir, "bench_test.go", tmpl, 100); err != nil {
+		return fmt.Errorf("failed to create good benchmark: %w", err)
+	}
+
+	_, err = w.Add("bench_test.go")
+	if err != nil {
+		return fmt.Errorf("failed to add bench_test.go: %w", err)
+	}
+
+	_, err = w.Commit("Add initial good benchmark", &git.CommitOptions{
+		Author: &object.Signature{
+			Name:  "Test User",
+			Email: "test@example.com",
+		},
+	})
+	if err != nil {
+		return fmt.Errorf("failed to commit initial benchmark: %w", err)
+	}
+
+	// Create worse benchmark (replacing the good one)
+	if err := createBenchmarkFile(dir, "bench_test.go", tmpl, 1000); err != nil {
+		return fmt.Errorf("failed to create worse benchmark: %w", err)
+	}
+
+	_, err = w.Add("bench_test.go")
+	if err != nil {
+		return fmt.Errorf("failed to add updated bench_test.go: %w", err)
+	}
+
+	_, err = w.Commit("Update with worse benchmark", &git.CommitOptions{
+		Author: &object.Signature{
+			Name:  "Test User",
+			Email: "test@example.com",
+		},
+	})
+	if err != nil {
+		return fmt.Errorf("failed to commit worse benchmark: %w", err)
+	}
+
+	return nil
+}
+
+func createBenchmarkFile(dir, filename, tmpl string, iterations int) error {
+	t, err := template.New("bench").Parse(tmpl)
+	if err != nil {
+		return fmt.Errorf("failed to parse template: %w", err)
+	}
+
+	f, err := os.Create(filepath.Join(dir, filename))
+	if err != nil {
+		return fmt.Errorf("failed to create file: %w", err)
+	}
+	defer f.Close()
+
+	data := struct {
+		Iterations int
+	}{
+		Iterations: iterations,
+	}
+
+	if err := t.Execute(f, data); err != nil {
+		return fmt.Errorf("failed to execute template: %w", err)
+	}
+
+	return nil
+}