Ppx_expect is a framework for writing tests in OCaml, similar to Cram. Ppx_expect mimics the existing inline tests framework with the let%expect_test construct. The body of an expect-test can contain output-generating code, interleaved with %expect extension expressions to denote the expected output.

When run, these tests will pass iff the output matches what was expected. If a test fails, a corrected file with the suffix ".corrected" will be produced with the actual output, and the inline_tests_runner will output a diff.