refactor(test): use cmp.Diff for struct comparisons

Replace assert.Equal with cmp.Diff for struct comparisons to get better
error messages when tests fail. This makes it easier to see exactly which
fields differ.

Changes:
- Add google/go-cmp import (already in go.mod)
- Use cmp.Diff for GitHubContext comparisons
- Use cmp.Diff for SigningError comparisons
- Remove unused testEnv map variable

Benefits:
- Better test failure messages showing field-by-field diffs
- More idiomatic Go testing pattern for complex types
- Easier debugging when tests fail

Co-authored-by: Ona <[email protected]>

Author: leodido

pkg/leeway/signing/attestation_test.go

@@ -15,6 +15,7 @@ import (
 	"testing"
 
 	"github.com/gitpod-io/leeway/pkg/leeway/cache"
+	"github.com/google/go-cmp/cmp"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -640,28 +641,22 @@ func TestGetGitHubContext(t *testing.T) {
 	t.Setenv("GITHUB_SERVER_URL", "test-server")
 	t.Setenv("GITHUB_WORKFLOW_REF", "test-workflow")
 
-	testEnv := map[string]string{
-		"GITHUB_RUN_ID":       "test-run-id",
-		"GITHUB_RUN_NUMBER":   "test-run-number",
-		"GITHUB_ACTOR":        "test-actor",
-		"GITHUB_REPOSITORY":   "test-repo",
-		"GITHUB_REF":          "test-ref",
-		"GITHUB_SHA":          "test-sha",
-		"GITHUB_SERVER_URL":   "test-server",
-		"GITHUB_WORKFLOW_REF": "test-workflow",
+	// Test GetGitHubContext
+	got := GetGitHubContext()
+	want := &GitHubContext{
+		RunID:       "test-run-id",
+		RunNumber:   "test-run-number",
+		Actor:       "test-actor",
+		Repository:  "test-repo",
+		Ref:         "test-ref",
+		SHA:         "test-sha",
+		ServerURL:   "test-server",
+		WorkflowRef: "test-workflow",
 	}
 
-	// Test GetGitHubContext
-	ctx := GetGitHubContext()
-
-	assert.Equal(t, testEnv["GITHUB_RUN_ID"], ctx.RunID)
-	assert.Equal(t, testEnv["GITHUB_RUN_NUMBER"], ctx.RunNumber)
-	assert.Equal(t, testEnv["GITHUB_ACTOR"], ctx.Actor)
-	assert.Equal(t, testEnv["GITHUB_REPOSITORY"], ctx.Repository)
-	assert.Equal(t, testEnv["GITHUB_REF"], ctx.Ref)
-	assert.Equal(t, testEnv["GITHUB_SHA"], ctx.SHA)
-	assert.Equal(t, testEnv["GITHUB_SERVER_URL"], ctx.ServerURL)
-	assert.Equal(t, testEnv["GITHUB_WORKFLOW_REF"], ctx.WorkflowRef)
+	if diff := cmp.Diff(want, got); diff != "" {
+		t.Errorf("GetGitHubContext() mismatch (-want +got):\n%s", diff)
+	}
 }
 
 // TestGetGitHubContext_EmptyEnvironment tests with empty environment
@@ -677,16 +672,21 @@ func TestGetGitHubContext_EmptyEnvironment(t *testing.T) {
 	t.Setenv("GITHUB_WORKFLOW_REF", "")
 
 	// Test GetGitHubContext with empty environment
-	ctx := GetGitHubContext()
-
-	assert.Empty(t, ctx.RunID)
-	assert.Empty(t, ctx.RunNumber)
-	assert.Empty(t, ctx.Actor)
-	assert.Empty(t, ctx.Repository)
-	assert.Empty(t, ctx.Ref)
-	assert.Empty(t, ctx.SHA)
-	assert.Empty(t, ctx.ServerURL)
-	assert.Empty(t, ctx.WorkflowRef)
+	got := GetGitHubContext()
+	want := &GitHubContext{
+		RunID:       "",
+		RunNumber:   "",
+		Actor:       "",
+		Repository:  "",
+		Ref:         "",
+		SHA:         "",
+		ServerURL:   "",
+		WorkflowRef: "",
+	}
+
+	if diff := cmp.Diff(want, got); diff != "" {
+		t.Errorf("GetGitHubContext() with empty env mismatch (-want +got):\n%s", diff)
+	}
 }
 
 // TestSigningError tests the error types
@@ -942,12 +942,12 @@ func TestCategorizeError_ExistingSigningError(t *testing.T) {
 		Message:  "access denied",
 	}
 
-	result := CategorizeError("different.tar.gz", originalErr)
+	got := CategorizeError("different.tar.gz", originalErr)
 
 	// Should return the original error unchanged
-	assert.Equal(t, originalErr, result)
-	assert.Equal(t, ErrorTypePermission, result.Type)
-	assert.Equal(t, "test.tar.gz", result.Artifact) // Original artifact preserved
+	if diff := cmp.Diff(originalErr, got); diff != "" {
+		t.Errorf("CategorizeError() should preserve original error (-want +got):\n%s", diff)
+	}
 }
 
 // TestWithRetry_MaxAttemptsExceeded tests retry exhaustion