Tests emulation of the user agent.

Checking page navigator.userAgent
...overriding userAgent to "Test UA"
navigator.userAgent == Test UA
Header User-Agent: Test UA
...overriding userAgent again to "Another Test UA"
navigator.userAgent == Another Test UA
Header User-Agent: Another Test UA

Checking page navigator.language
...overriding acceptLanguage to "ko, en, zh-CN, zh-HK, en-US, en-GB"
navigator.language == ko
navigator.languages == ko,en,zh-CN,zh-HK,en-US,en-GB
...overriding acceptLanguage to "en, zh-CN, zh-HK, en-US, en-GB"
navigator.language == en
navigator.languages == en,zh-CN,zh-HK,en-US,en-GB

Checking worker navigator.language
...overriding acceptLanguage to "ko, en, zh-CN, zh-HK, en-US, en-GB"
workerNavigator.language == ko
workerNavigator.languages == ko,en,zh-CN,zh-HK,en-US,en-GB
...overriding acceptLanguage to "en, zh-CN, zh-HK, en-US, en-GB"
workerNavigator.language == en
workerNavigator.languages == en,zh-CN,zh-HK,en-US,en-GB

Checking Accept-Language header
...overriding acceptLanguage to "ko, en, zh-CN, zh-HK, en-US, en-GB"
Header Accept-Language: en, zh-CN;q=0.9, zh-HK;q=0.8, en-US;q=0.7, en-GB;q=0.6
Fetch with custom header accept-language: zh-CN
...overriding acceptLanguage to "en, zh-CN, zh-HK, en-US, en-GB"
Header Accept-Language: en, zh-CN;q=0.9, zh-HK;q=0.8, en-US;q=0.7, en-GB;q=0.6
Fetch with custom header accept-language: zh-CN

Checking page navigator.platform
...setting platform to "new_platform"
navigator.platform == new_platform
...setting platform again to "another_platform"
navigator.platform == another_platform