A function which, when evaluated, produces a list of expectations. Also a list of labels which apply to this outcome.

Test Runners which have had seeds distributed to them, and which are now either invalid or are ready to run. Seeded runners include some metadata:

• Invalid runners had a problem (e.g. two sibling tests had the same description) making them un-runnable.
• Only runners can be run, but Test.only was used somewhere, so ultimately they will lead to a failed test run even if each test that gets run passes.
• Skipping runners can be run, but Test.skip was used somewhere, so ultimately they will lead to a failed test run even if each test that gets run passes.
• Plain runners are ready to run, and have none of these issues.

Convert a Test into SeededRunners.

In order to run any fuzz tests that the Test may have, it requires a default run count as well as an initial Random.Seed. 100 is a good run count. To obtain a good random seed, pass a random 32-bit integer to Random.initialSeed. You can obtain such an integer by running Math.floor(Math.random()*0xFFFFFFFF) in Node. It's typically fine to hard-code this value into your Elm code; it's easy and makes your tests reproducible.

Return Nothing if the given Expectation is a pass.

If it is a fail, return a record containing the expectation description, the Reason the test failed, and the given inputs if it was a fuzz test. (If it was not a fuzz test, the record's given field will be Nothing).

For example:

getFailureReason (Expect.equal 1 2)
-- Just { reason = Equal 1 2, description = "Expect.equal", given = Nothing }


getFailureReason (Expect.equal 1 1)
-- Nothing

Determine if an expectation was created by a call to Test.todo. Runners may treat these tests differently in their output.

A standard way to format descriptions and test labels, to keep things consistent across test runner implementations.

The HTML, Node, String, and Log runners all use this.

What it does:

• drop any labels that are empty strings
• format the first label differently from the others
• reverse the resulting list

Example:

[ "the actual test that failed"
, "nested description failure"
, "top-level description failure"
]
|> formatLabels ((++) "↓ ") ((++) "✗ ")


{-
[ "↓ top-level description failure"
, "↓ nested description failure"
, "✗ the actual test that failed"
]
-}

A Shrinkable a is an opaque type that allows you to obtain a value of type a that is smaller than the one you've previously obtained.

Given a fuzzer, return a random generator to produce a value and a Shrinkable. The value is what a fuzz test would have received as input.

Given a Shrinkable, attempt to shrink the value further. Pass False to indicate that the last value you've seen (from either fuzz or this function) caused the test to fail. This will attempt to find a smaller value. Pass True if the test passed. If you have already seen a failure, this will attempt to shrink that failure in another way. In both cases, it may be impossible to shrink the value, represented by Nothing.