# Context `VerifySettings.Context` is a dictionary that carries information from a test to the extension points that run during a verification. It is exposed as `IReadOnlyDictionary` to: * [Comparers](/docs/comparer.md) * [Converters](/docs/converter.md) * [Scrubbers](/docs/scrubbers.md) * [AppendFile](/docs/append-file.md) and [JsonAppender](/docs/jsonappender.md) delegates It is also exposed as `VerifyJsonWriter.Context` to serialization converters. Those extension points are registered globally, and are shared by every test. Context is how a single test passes state to them, for example an environment name or a feature flag. Values are written to the dictionary on the settings used for the verification: ```cs [Fact] public Task ComparerWithContext() { var settings = new VerifySettings { Context = { ["featureEnabled"] = true } }; settings.UseStringComparer(Compare, "txt"); return Verify("TheText", settings); } ``` ^{snippet source | anchor} Or fluently, via `AddContext`: ```cs [Fact] public Task ComparerWithContextFluent() => Verify("TheText") .AddContext("featureEnabled", true) .UseStringComparer(Compare, "txt"); ``` ^{snippet source | anchor} And read in the extension point: ```cs static Task Compare( string received, string verified, IReadOnlyDictionary context) { if (context.TryGetValue("featureEnabled", out var value) && value is true) { // Drop the flagged content from both sides before comparing return Task.FromResult( new CompareResult(RemoveFlagged(received) == RemoveFlagged(verified))); } return Task.FromResult(new CompareResult(received == verified)); } static string RemoveFlagged(string value) => string.Join( '\n', value .Split('\n') .Where(_ => !_.Contains("FeatureFlagged"))); ``` ^{snippet source | anchor} Values that are the same for every test do not need Context. A static field is sufficient in that case. Context matters where the value varies per test. ## Reserved keys Verify uses the same dictionary for some per-verification state, under keys prefixed with `Verify.`. For example `ExcludeTargets` stores its extensions under `Verify.ExcludeTargets`, which is what allows a converter to call `context.IsTargetExcluded("png")`. Keys prefixed with `Verify.` should be treated as reserved. ## Copy behavior When settings are copied, for example when a `VerifySettings` instance is passed to a fluent API, the context is copied entry by entry. Entries implementing `ICloneable` are cloned, and all other entries are copied by reference.