Unit testing an analyzer

To help analyzer authors testing their analyzers, there's a dedicated testing package. It contains easy to use utility functions to create a context for the analyzer and assertion helpers.

FSharp.Analyzers.SDK.Testing.mkOptionsFromProject creates the FSharpProjectOptions for the given framework (e.g. net7.0) and the given list of packages to reference. FSharp.Analyzers.SDK.Testing.getContext then takes the FSharpProjectOptions and the source code to test and creates a CliContext you can pass along to your analyzer function. The module FSharp.Analyzers.SDK.Testing.Assert offers various functions to help with assertion statements from your favorite unit testing framework. For a complete example of an unit testing project, take a look at OptionAnalyzer.Test in the samples folder of the SDK repository.

open FSharp.Compiler.CodeAnalysis
open FSharp.Analyzers.SDK.Testing
open OptionAnalyzer
open NUnit.Framework

let mutable projectOptions: FSharpProjectOptions = FSharpProjectOptions.zero

[<SetUp>]
let Setup () =
    task {
        let! opts =
            mkOptionsFromProject
                "net7.0"
                [
                  // The SDK uses this in a "dotnet add package x --version y" command
                  // to generate the needed FSharpProjectOptions
                  { Name = "Newtonsoft.Json"
                    Version = "13.0.3" } ]

        projectOptions <- opts
    }

[<Test>]
let ``warnings are emitted`` () =
    async {
        let source =
            """
module M

let notUsed() =
    let option : Option<int> = None
    option.Value
    """

        let ctx = getContext projectOptions source
        let! msgs = optionValueAnalyzer ctx
        Assert.IsNotEmpty msgs
        Assert.IsTrue(Assert.messageContains "Option.Value" msgs[0])
    }

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