Yes. Once you open a test, you cannot pause the test.
If you close the test popup window it is counted as an attempt, even if you only read the title slide.
Each test is of short duration though, so planning prior to opening a test will alleviate most issues.
Test Duration
The majority of tests are only approximately 2-5 minutes each. The test conditions require that they are completed in one sitting to avoid opportunities for cheating to occur. Each test question also has a time limit for your response.