feat: add version checker test

tuf/version.go

@@ -33,14 +33,17 @@ func (e *InvalidVersionError) Error() string {
 }
 
 func NewDefaultVersionChecker() *DefaultVersionChecker {
-	return &DefaultVersionChecker{}
+	return &DefaultVersionChecker{
+		VersionFetcher: version.NewGoVersionFetcher(),
+	}
 }
 
-type DefaultVersionChecker struct{}
+type DefaultVersionChecker struct {
+	VersionFetcher version.Fetcher
+}
 
 func (vc *DefaultVersionChecker) CheckVersion(client Downloader) error {
-	fetcher := version.NewGoVersionFetcher()
-	attestVersion, err := fetcher.Get()
+	attestVersion, err := vc.VersionFetcher.Get()
 	if err != nil {
 		return fmt.Errorf("failed to get version: %w", err)
 	}

tuf/version_test.go

@@ -0,0 +1,61 @@
+package tuf
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/Masterminds/semver/v3"
+	"github.com/docker/attest/internal/test"
+	"github.com/docker/attest/version"
+	"github.com/stretchr/testify/assert"
+)
+
+const (
+	invalidVersion    = "0.0.1"
+	validVersion      = "v1.0.0-0"
+	versionConstraint = ">=v1.0.0-0"
+)
+
+func TestDefaultVersionChecker(t *testing.T) {
+	testDir := test.CreateTempDir(t, "", "tuf_temp")
+	versionConstraintsPath := filepath.Join(testDir, "version-constraints")
+	err := os.WriteFile(versionConstraintsPath, []byte(versionConstraint), 0o600)
+	assert.NoError(t, err)
+	tufClient := NewMockTufClient(testDir)
+
+	expectedError := fmt.Sprintf("%s version %s does not satisfy constraints %s: %s is less than %s", version.ThisModulePath, invalidVersion, versionConstraint, invalidVersion, validVersion)
+
+	testCases := []struct {
+		name          string
+		expectedError string
+		version       string
+	}{
+		{name: "version is less than the minimum", expectedError: expectedError, version: "0.0.1"},
+		{name: "version is equal to the minimum", version: "1.0.0"},
+		{name: "version is greater than the minimum", version: "1.0.1"},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			checker := NewDefaultVersionChecker()
+			checker.VersionFetcher = &MockVersionFetcher{version: tc.version}
+			err := checker.CheckVersion(tufClient)
+			if tc.expectedError != "" {
+				assert.Error(t, err)
+				assert.Equal(t, tc.expectedError, err.Error())
+				return
+			}
+			assert.NoError(t, err)
+		})
+	}
+}
+
+type MockVersionFetcher struct {
+	version string
+}
+
+func (m *MockVersionFetcher) Get() (*semver.Version, error) {
+	return semver.NewVersion(m.version)
+}