[Test]Add unit test for platform.py (#1476)

### What this PR does / why we need it?
According to issue #1298 , this pull request adds unit test code for
platform.py.

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
CI passed with new added/existing test.

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Signed-off-by: zhanghw0354 <zhanghaiwen_yewu@cmss.chinamobile.com>
Signed-off-by: shen-shanshan <467638484@qq.com>
Signed-off-by: MengqingCao <cmq0113@163.com>
Signed-off-by: Yikun Jiang <yikunkero@gmail.com>
Signed-off-by: angazenn <zengyanjia@huawei.com>
Signed-off-by: zhuyilin <809721801@qq.com>
Co-authored-by: Shanshan Shen <467638484@qq.com>
Co-authored-by: Mengqing Cao <cmq0113@163.com>
Co-authored-by: Yikun Jiang <yikunkero@gmail.com>
Co-authored-by: Angazenn <92204292+Angazenn@users.noreply.github.com>
Co-authored-by: angazenn <zengyanjia@huawei.com>
Co-authored-by: Zhu Yi Lin <116337067+GDzhu01@users.noreply.github.com>

Author: 7 people