A test runner discovers tests, executes them, and reports their results. In F#, it can connect automated tests with IDEs such as Visual Studio or run them from the command line. section 14.2 section 14.4
Expecto treats tests as ordinary F# values: individual tests or nested lists can be composed, selected, generated, and passed to the runner. This avoids classes, inheritance, and attributes, while allowing conditions such as CI-only tests or data-driven repetition. section 14.2.4
Programmatic test generation
A test list can read rows from testData.txt, create an addition test for each row, and decide whether to include a CI-only test from an environment variable. The runner reports each generated test and summarizes passes, failures, and errors. section 14.2.4
XUnit uses a more conventional discovery model. Tests usually live in a class library, carry attributes such as [<Fact>], and run through dotnet test. This reduces manual composition but binds discovery and execution to the framework. section 14.4
Listing 14.4 Programmatically creating tests in Expecto
let add a b = a + b #1 let myTests = testList "My Tests" [ if System.Environment.GetEnvironmentVariable "CI_SERVER" <> null then #2 test "CI Only Test" { Expect.equal (add 1 2) 3 "Something is very wrong!" } for line in System.IO.File.ReadAllLines "testData.txt" do #3 test $"Addition test: {line}" { #4 match line.Split ',' with | [| inputA; inputB; expected |] -> let actual = add (int inputA) (int inputB) Expect.equal actual (int expected) "Calculator is broken" | _ -> failwith $"Invalid test data format: {line}" } ] #1 Our production code, a simple addition function #2 Programmatically decides whether to yield back a test based on the existence of an environment variable #3 Reads data from a file using basic .NET code #4 For each line in the file, yields back a new test whose name is based on the line in the file
Inspect a complete Expecto example that builds tests from CI conditions and input-file rows. section 14.2.4
