Fix file creation for output options (#875)

test/cli/packages_cmd_test.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"fmt"
+	"path/filepath"
 	"strings"
 	"testing"
 )
@@ -192,6 +193,26 @@ func TestPackagesCmdFlags(t *testing.T) {
 				assertSuccessfulReturnCode,
 			},
 		},
+		{
+			name: "json-file-flag",
+			args: []string{"packages", "-o", "json", "--file", filepath.Join(tmp, "output-1.json"), coverageImage},
+			assertions: []traitAssertion{
+				assertSuccessfulReturnCode,
+				assertFileOutput(t, filepath.Join(tmp, "output-1.json"),
+					assertJsonReport,
+				),
+			},
+		},
+		{
+			name: "json-output-flag-to-file",
+			args: []string{"packages", "-o", fmt.Sprintf("json=%s", filepath.Join(tmp, "output-2.json")), coverageImage},
+			assertions: []traitAssertion{
+				assertSuccessfulReturnCode,
+				assertFileOutput(t, filepath.Join(tmp, "output-2.json"),
+					assertJsonReport,
+				),
+			},
+		},
 	}
 
 	for _, test := range tests {

test/cli/trait_assertions_test.go

@@ -10,10 +10,26 @@ import (
 	"testing"
 
 	"github.com/acarl005/stripansi"
+	"github.com/stretchr/testify/require"
 )
 
 type traitAssertion func(tb testing.TB, stdout, stderr string, rc int)
 
+func assertFileOutput(tb testing.TB, path string, assertions ...traitAssertion) traitAssertion {
+	tb.Helper()
+
+	return func(tb testing.TB, _, stderr string, rc int) {
+		content, err := os.ReadFile(path)
+		require.NoError(tb, err)
+		contentStr := string(content)
+
+		for _, assertion := range assertions {
+			// treat the file content as stdout
+			assertion(tb, contentStr, stderr, rc)
+		}
+	}
+}
+
 func assertJsonReport(tb testing.TB, stdout, _ string, _ int) {
 	tb.Helper()
 	var data interface{}