         transcribeFileDefault(filename: "SpeechSample", withExtension: "flac", format: "audio/flac")
     }
 
-    func transcribeFileDefault(filename: String, withExtension: String, format: String) {
+    func testTranscribeFileNoFormat() {
+        transcribeFileDefault(filename: "SpeechSample", withExtension: "wav", format: nil)
+    }
+
+    func transcribeFileDefault(filename: String, withExtension: String, format: String?) {
         let description = "Transcribe an audio file."
         let expectation = self.expectation(description: description)
 

        transcribeDataDefault(filename: "SpeechSample", withExtension: "flac", format: "audio/flac")
    }

    func transcribeDataDefault(filename: String, withExtension: String, format: String) {
        let description = "Transcribe an audio file."
        let expectation = self.expectation(description: description)


        transcribeFileCustom(filename: "SpeechSample", withExtension: "flac", format: "audio/flac")
    }

    func testTranscribeFileCustomNoFormat() {
        transcribeFileCustom(filename: "SpeechSample", withExtension: "ogg", format: nil)
    }

    func transcribeFileCustom(filename: String, withExtension: String, format: String?) {
        let description = "Transcribe an audio file."
        let expectation = self.expectation(description: description)

