Steps to reproduce:
1. Have a jenkins job with IM plugin enabled to send notifications (with Jabber in our case)
2. Set up a test that fails which contains a space in the name
3. Run test and Jenkins IM plugin will send the notification

Expected result:
3. Correct link to the failed test

Actual result:
3. Link to the test is incorrect, since it contains non url-encoded characters.

In the example in the screenshot you can see that the Jabber client automatically creates a link to the test, but fails at the first space (after "Price" in "Price type rules").

Possible solution:
I have identified where in the code the URL is built:

• MessageHelper.getTestUrl() for building the url to the failing test
• MessageHelper.getBuildURL() for building the base link (and the link to the build)

https://github.com/jenkinsci/instant-messaging-plugin/blob/master/src/main/java/hudson/plugins/im/tools/MessageHelper.java?source=cc

It seems that there is some encoding done in getBuildURL() but not in getTestUrl()?

And here's where it is used to build the full string sent:
https://github.com/jenkinsci/instant-messaging-plugin/blob/29e24e0f1e5714749a479b6e5c4224c3ac66b701/src/main/java/hudson/plugins/im/build_notify/PrintFailingTestsBuildToChatNotifier.java#L87-L95