This Limits Documentation mentions:
Total number of test classes that can be queued per a 24-hour period (5) - The greater of 500 or 10 multiplied by the number of test classes in the organization
with the caveat that
This limit applies to tests running asynchronously. This includes tests started through the Salesforce user interface including the Developer Console or by inserting
ApexTestQueueItemobjects using SOAP API.
- What qualifies as running a test synchronously?
- How can I ensure that my team members working concurrently in a sandbox do not exceed the AsyncApexTests Limit while building, refining and executing unit tests? (This quickly brings test development to a grinding halt.)
- Does running tests via the Eclipse "run tests" menu option kick off an async or synchronous test run?
An update that is a bit like an answer:
If you need to run a unit test synchronously, you can do so in the developer console's run tests UI by selecting just a single class to run. Selecting two or more classes will execute them asynchronously.
This makes receiving the
AsyncApexTests Limit exceeded exception a little bit more bearable and less blocking.
The Developer Console runs tests asynchronously in the background, unless your test run includes only one class and you’ve not chosen Always Run Asynchronously in the Test menu.