Diffblue

Diffblue builds software that writes Java unit tests automatically, aimed at enterprise teams that need test coverage in large or aging codebases. The company says its tools cut the hand-written test work that slows development and holds up releases.

The Diffblue Testing Agent

The flagship offering is the Diffblue Testing Agent, which runs on top of the approved AI coding tools a customer already uses rather than replacing them. It coordinates the whole test-writing job: analyzing coverage, fixing build problems, planning which tests to write, generating tests in parallel, verifying the output, cleaning up the project and preparing a pull request. The company says this orchestration is what turns raw AI output into tests a team would be willing to merge.

Diffblue Cover and continuous integration

Diffblue Cover is the company's tool for writing Java unit tests and keeping them up to date as the code changes. Teams can run it as an automatic step in continuous integration pipelines, so coverage checks stop depending on how much time a developer has to write tests. The company says it can write a unit test in a few seconds, which it contrasts with the roughly ten minutes it says a developer needs to write and evaluate one by hand.

Modernizing legacy Java systems

Enterprises moving older applications to the cloud often inherit code that is poorly documented and lightly tested. The company says a baseline of regression tests can be produced in hours, giving teams a safety net before they change anything. It says the agent handles legacy Java 8 and 11 codebases that general AI coding tools tend to struggle with.

Benchmark results the company reports

Diffblue describes an internal benchmark across eight enterprise Java repositories totaling 31,069 coverable lines, all starting from zero percent coverage. It compares the agent with a senior developer using Claude Code, and reports that one customer project of about 20,000 lines reached coverage in roughly 510 minutes. These are the company's own figures, and its benchmark methodology is set out alongside the results.

Who the product is for

The tools suit enterprise development groups that work in Java, particularly those facing a shift-left testing approach or a modernization program. The company says it works with a customer's approved AI platform, with no separate model vendor to evaluate, and that the product carries about ten years of test-writing know-how.