Doing one test for a language should not validate it

[raxod502]

Currently, whenever you do at least one test for a language, and it passes, a file is written to disk that certifies passing tests for that language. This is then tracked by Depgraph. However, really what this file should signify is that all tests are passing for a language. We need to slightly modify the logic in test-runner.js to refrain from certifying a test result unless all tests were run for the given language.