add mix test in test_cli.sh, test=tts

tests/unit/cli/test_cli.sh

@@ -53,6 +53,12 @@ paddlespeech tts --am fastspeech2_vctk --voc hifigan_vctk --input "Life was like
 paddlespeech tts --am tacotron2_csmsc --input "你好，欢迎使用百度飞桨深度学习框架！"
 paddlespeech tts --am tacotron2_csmsc --voc wavernn_csmsc --input "你好，欢迎使用百度飞桨深度学习框架！"
 paddlespeech tts --am tacotron2_ljspeech --voc pwgan_ljspeech --lang en --input "Life was like a box of chocolates, you never know what you're gonna get."
+# mix tts
+# The `am` must be `fastspeech2_mix`!
+# The `lang` must be `mix`!
+# The voc must be `hifigan_ljspeech` or `pwgan_ljspeech` for f`astspeech2_mix` now!
+paddlespeech tts --am fastspeech2_mix --voc hifigan_ljspeech --lang mix  --input "热烈欢迎您在 Discussions 中提交问题，并在 Issues 中指出发现的 bug。此外，我们非常希望您参与到 Paddle Speech 的开发中！" --spk_id 0  --output mix_spk0.wav
+paddlespeech tts --am fastspeech2_mix --voc pwgan_ljspeech --lang mix  --input "我们的声学模型使用了 Fast Speech Two, 声码器使用了 Parallel Wave GAN and Hifi GAN." --spk_id 1  --output mix_spk1.wav
 
 # Speech Translation (only support linux)
 paddlespeech st --input ./en.wav