AI Can Write Tests Faster Than Your Team Can Understand Them
AI coding tools have solved one problem remarkably well: They can produce code extremely quickly. That sounds obviously good. And most of the time, it is. But software development has never really been constrained by how fast we can type. The expensive part comes later. Understanding the code. Reviewing it. Debugging it. Changing it six months later when the person—or model—that wrote it has forgotten why it exists. Test automation is where this becomes especially interesting. Generating the Test Is the Cheap Part You can ask an AI coding assistant: Write Playwright tests for our signup, login, checkout, password reset, dashboard, invoices, settings, and admin pages. And a few minutes later you might have hundreds or thousands of lines of test code. It feels like incredible leverage. Until the suite starts failing. That’s the argument behind looking at the hidden cost of AI-generated test code . Generation cost has collapsed. Maintenance cost hasn’t. In some cases, AI actually increases it because you now have more code than your team would have written manually. AI Pull Requests Need Different Review There’s another subtle problem. Humans tend to judge large AI-generated pull requests differently. When someone on your team writes 80 lines, you probably read them. When an AI assistant generates 1,800 lines? You skim. You look at the filenames. You check whether CI is green. Merge. That’s dangerous for normal application code and potentially worse for test code because a bad test can happily pass for months. There are good ideas in this guide to testing AI coding assistant pull requests , but the bigger principle is simple: AI-generated tests need validation just like AI-generated product code. “Generated successfully” does not mean “tests the right thing.” Agents Add Another Failure Mode Now we’re moving from AI that writes test code to AI that actually decides what actions to take. That introduces a new question: What if the model chooses the wrong tool? An agent m