diff --git a/cmd/substation/test.go b/cmd/substation/test.go
index be7263b7..0a4bef1a 100644
--- a/cmd/substation/test.go
+++ b/cmd/substation/test.go
@@ -203,6 +203,8 @@ func testFile(arg string, extVars map[string]string) error {
 	fileName := filepath.Base(arg)
 	_ = os.Chdir(filepath.Dir(arg))
 
+	// The default case is a no-op -- the file is skipped because
+	// it cannot be tested.
 	switch filepath.Ext(fileName) {
 	case ".jsonnet", ".libsonnet":
 		// If the Jsonnet cannot compile, then the file is invalid.
diff --git a/cmd/substation/vet.go b/cmd/substation/vet.go
index ab7dab7b..671ade42 100644
--- a/cmd/substation/vet.go
+++ b/cmd/substation/vet.go
@@ -104,6 +104,8 @@ func vetFile(arg string, extVars map[string]string) error {
 	fileName := filepath.Base(arg)
 	_ = os.Chdir(filepath.Dir(arg))
 
+	// The default case is a no-op -- the file is skipped because
+	// it cannot be vetted.
 	switch filepath.Ext(fileName) {
 	case ".jsonnet", ".libsonnet":
 		mem, err := compileFile(fileName, extVars)