# I'm getting an error "failed: AttributeError: type object 'DesiredCapabilities' has no attribute 'OPERA'" using SeleniumTestability

**URL:** <https://forum.robotframework.org/t/im-getting-an-error-failed-attributeerror-type-object-desiredcapabilities-has-no-attribute-opera-using-seleniumtestability/5204>\
**Category:** SeleniumLibrary\
**Created:** [25 January 2023 04:12 UTC](https://forum.robotframework.org/t/im-getting-an-error-failed-attributeerror-type-object-desiredcapabilities-has-no-attribute-opera-using-seleniumtestability/5204 "2023-01-25T04:12:26Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![nyxalexa](https://dub1.discourse-cdn.com/flex005/user_avatar/forum.robotframework.org/nyxalexa/32/1726_2.png) [@nyxalexa](https://forum.robotframework.org/u/nyxalexa)\
**Post date:** [25 January 2023 04:12 UTC](https://forum.robotframework.org/t/im-getting-an-error-failed-attributeerror-type-object-desiredcapabilities-has-no-attribute-opera-using-seleniumtestability/5204/1 "2023-01-25T04:12:26Z")

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My tests are working on my Linux machine, but once I moved to Mac, i’m getting an error.

[ERROR] Error. … on line 4: Initializing library ‘SeleniumLibrary’ with arguments [plugins=SeleniumTestability;True;30 Seconds;True] failed: Importing test library ‘SeleniumTestability’ failed: AttributeError: type object ‘DesiredCapabilities’ has no attribute ‘OPERA’

Library: [https://marketsquare.github.io/robotframework-seleniumtestability/index.html?tag=plugin#Get%20Default%20Capabilities](https://marketsquare.github.io/robotframework-seleniumtestability/index.html?tag=plugin#Get%20Default%20Capabilities)

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**Author:** ![aaltat](https://dub1.discourse-cdn.com/flex005/user_avatar/forum.robotframework.org/aaltat/32/15_2.png) [@aaltat](https://forum.robotframework.org/u/aaltat)\
**Post date:** [25 January 2023 21:36 UTC](https://forum.robotframework.org/t/im-getting-an-error-failed-attributeerror-type-object-desiredcapabilities-has-no-attribute-opera-using-seleniumtestability/5204/2 "2023-01-25T21:36:39Z")

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Opera is not supported with resent versions of Selenium. You need to find Selenium version which supports Opera and SeleniumLibrary which supports that version of Selenium.

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**Author:** ![nyxalexa](https://dub1.discourse-cdn.com/flex005/user_avatar/forum.robotframework.org/nyxalexa/32/1726_2.png) [@nyxalexa](https://forum.robotframework.org/u/nyxalexa)\
**Post date:** [25 January 2023 21:50 UTC](https://forum.robotframework.org/t/im-getting-an-error-failed-attributeerror-type-object-desiredcapabilities-has-no-attribute-opera-using-seleniumtestability/5204/3 "2023-01-25T21:50:36Z")

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I see, thank you.

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<div class="post-metadata">

**Author:** ![nyxalexa](https://dub1.discourse-cdn.com/flex005/user_avatar/forum.robotframework.org/nyxalexa/32/1726_2.png) [@nyxalexa](https://forum.robotframework.org/u/nyxalexa)\
**Post date:** [26 January 2023 02:22 UTC](https://forum.robotframework.org/t/im-getting-an-error-failed-attributeerror-type-object-desiredcapabilities-has-no-attribute-opera-using-seleniumtestability/5204/4 "2023-01-26T02:22:21Z")

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I was able to fix this by installing version selenium=4.2.0