test: use diff module (#202)

go.mod

@@ -5,6 +5,7 @@ go 1.17
 require (
 	github.com/BurntSushi/toml v1.0.0
 	github.com/fatih/color v1.13.0
+	github.com/google/go-cmp v0.5.9
 	golang.org/x/mod v0.5.1
 	gopkg.in/yaml.v2 v2.4.0
 )

go.sum

@@ -2,6 +2,8 @@ github.com/BurntSushi/toml v1.0.0 h1:dtDWrepsVPfW9H/4y7dDgFc2MBUSeJhlaDtK13CxFlU
 github.com/BurntSushi/toml v1.0.0/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
 github.com/fatih/color v1.13.0 h1:8LOYc1KYPPmyKMuN8QV2DNRWNbLo6LZ0iLs8+mlH53w=
 github.com/fatih/color v1.13.0/go.mod h1:kLAiJbzzSOZDVNGyDpeOxJ47H46qBXwg5ILebYFFOfk=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/mattn/go-colorable v0.1.9 h1:sqDoxXbdeALODt0DAeJCVp38ps9ZogZEAXjus69YV3U=
 github.com/mattn/go-colorable v0.1.9/go.mod h1:u6P/XSegPjTcexA+o6vUJrdnUu04hMope9wVRipJSqc=
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=

main_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"bytes"
 	"fmt"
+	"github.com/google/go-cmp/cmp"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -80,6 +81,21 @@ func normalizeFilePaths(output string) string {
 	return strings.ReplaceAll(strings.ReplaceAll(output, "\\\\", "/"), "\\", "/")
 }
 
+func expectAreEqual(t *testing.T, subject, actual, expect string) {
+	t.Helper()
+
+	actual = dedent(t, actual)
+	expect = dedent(t, expect)
+
+	if !areEqual(t, actual, expect) {
+		if os.Getenv("TEST_NO_DIFF") == "true" {
+			t.Errorf("\nactual %s does not match expected:\n got:\n%s\n\n want:\n%s", subject, actual, expect)
+		} else {
+			t.Errorf("\nactual %s does not match expected:\n%s", subject, cmp.Diff(expect, actual))
+		}
+	}
+}
+
 func testCli(t *testing.T, tc cliTestCase) {
 	t.Helper()
 
@@ -95,13 +111,8 @@ func testCli(t *testing.T, tc cliTestCase) {
 		t.Errorf("cli exited with code %d, not %d", ec, tc.wantExitCode)
 	}
 
-	if !areEqual(t, dedent(t, stdout), dedent(t, tc.wantStdout)) {
-		t.Errorf("stdout\n got:\n%s\n\n want:\n%s", dedent(t, stdout), dedent(t, tc.wantStdout))
-	}
-
-	if !areEqual(t, dedent(t, stderr), dedent(t, tc.wantStderr)) {
-		t.Errorf("stderr\n got:\n%s\n\n want:\n%s", dedent(t, stderr), dedent(t, tc.wantStderr))
-	}
+	expectAreEqual(t, "stdout output", stdout, tc.wantStdout)
+	expectAreEqual(t, "stderr output", stderr, tc.wantStderr)
 }
 
 func TestRun(t *testing.T) {

pkg/database/dir_test.go

@@ -3,6 +3,7 @@ package database_test
 import (
 	"errors"
 	"github.com/g-rath/osv-detector/pkg/database"
+	"github.com/google/go-cmp/cmp"
 	"reflect"
 	"testing"
 )
@@ -79,6 +80,6 @@ func TestNewDirDB_WorkingDirectory(t *testing.T) {
 	}
 
 	if !reflect.DeepEqual(db.Vulnerabilities(false), osvs) {
-		t.Errorf("db is missing some vulnerabilities: %v vs %v", db.Vulnerabilities(false), osvs)
+		t.Errorf("db is missing some vulnerabilities:\n%s", cmp.Diff(db.Vulnerabilities(false), osvs))
 	}
 }

pkg/database/zip_test.go

@@ -8,6 +8,7 @@ import (
 	"errors"
 	"fmt"
 	"github.com/g-rath/osv-detector/pkg/database"
+	"github.com/google/go-cmp/cmp"
 	"net/http"
 	"net/http/httptest"
 	"os"
@@ -36,7 +37,7 @@ func expectDBToHaveOSVs(
 	})
 
 	if !reflect.DeepEqual(vulns, actual) {
-		t.Errorf("db is missing some vulnerabilities: %v vs %v", vulns, actual)
+		t.Errorf("db is missing some vulnerabilities:\n%s", cmp.Diff(vulns, actual))
 	}
 }