Add --group flag to override group name for stdin input

- Add --group CLI flag to test command for custom group naming
- Override FileName from '-' to custom group name when --group is provided
- Enables better identification of policy violations in CI/CD workflows
- Add unit tests for group flag functionality

Fixes #1095

Author: nikos.nikolakakis

internal/commands/test.go

@@ -115,6 +115,7 @@ func NewTestCommand(ctx context.Context) *cobra.Command {
 				"junit-hide-message",
 				"quiet",
 				"tls",
+				"group",
 			}
 			for _, name := range flagNames {
 				if err := viper.BindPFlag(name, cmd.Flags().Lookup(name)); err != nil {
@@ -196,6 +197,7 @@ func NewTestCommand(ctx context.Context) *cobra.Command {
 
 	cmd.Flags().StringSlice("proto-file-dirs", []string{}, "A list of directories containing Protocol Buffer definitions")
 	cmd.Flags().Bool("tls", true, "Use TLS to access the registry")
+	cmd.Flags().String("group", "", "Override the group name for stdin input (used for output formatting)")
 
 	return &cmd
 }

runner/test.go

@@ -35,6 +35,7 @@ type TestRunner struct {
 	Combine            bool
 	Quiet              bool
 	Output             string
+	Group              string
 }
 
 // Run executes the TestRunner, verifying all Rego policies against the given
@@ -110,6 +111,15 @@ func (t *TestRunner) Run(ctx context.Context, fileList []string) (output.CheckRe
 		}
 	}
 
+	// Override group name for stdin input if --group flag is provided
+	if t.Group != "" {
+		for i := range results {
+			if results[i].FileName == "-" {
+				results[i].FileName = t.Group
+			}
+		}
+	}
+
 	return results, nil
 }
 

runner/test_test.go

@@ -0,0 +1,77 @@
+package runner
+
+import (
+	"testing"
+
+	"github.com/open-policy-agent/conftest/output"
+)
+
+func TestTestRunner_GroupFlag(t *testing.T) {
+	// Create a mock TestRunner with Group set
+	runner := TestRunner{
+		Group: "my-custom-group",
+	}
+
+	// Create mock results with stdin filename
+	results := output.CheckResults{
+		{
+			FileName:  "-",
+			Namespace: "main",
+			Failures:  []output.Result{{Message: "test failure"}},
+		},
+		{
+			FileName:  "regular-file.yaml",
+			Namespace: "main", 
+			Failures:  []output.Result{{Message: "another failure"}},
+		},
+	}
+
+	// Test the group name override logic
+	if runner.Group != "" {
+		for i := range results {
+			if results[i].FileName == "-" {
+				results[i].FileName = runner.Group
+			}
+		}
+	}
+
+	// Verify the stdin result was updated
+	if results[0].FileName != "my-custom-group" {
+		t.Errorf("Expected stdin filename to be overridden to 'my-custom-group', got '%s'", results[0].FileName)
+	}
+
+	// Verify the regular file result was not changed
+	if results[1].FileName != "regular-file.yaml" {
+		t.Errorf("Expected regular filename to remain 'regular-file.yaml', got '%s'", results[1].FileName)
+	}
+}
+
+func TestTestRunner_GroupFlagEmpty(t *testing.T) {
+	// Create a mock TestRunner without Group set
+	runner := TestRunner{
+		Group: "",
+	}
+
+	// Create mock results with stdin filename
+	results := output.CheckResults{
+		{
+			FileName:  "-",
+			Namespace: "main",
+			Failures:  []output.Result{{Message: "test failure"}},
+		},
+	}
+
+	// Test the group name override logic
+	if runner.Group != "" {
+		for i := range results {
+			if results[i].FileName == "-" {
+				results[i].FileName = runner.Group
+			}
+		}
+	}
+
+	// Verify the stdin result was NOT updated
+	if results[0].FileName != "-" {
+		t.Errorf("Expected stdin filename to remain '-', got '%s'", results[0].FileName)
+	}
+}