Elsa Core

October 29, 2025 · View on GitHub

Purpose

This document is a practical test guideline. It tells you what to test, when to test it, and how to write deterministic, actionable tests using the repository's existing test helpers and patterns.

Summary

The philosophy of testing in Elsa can be summarized as:

Whenever a test fails, it should provide a clear direction towards the cause of the problem.

Tests should be fast, deterministic, and precise: they should pinpoint the failing subsystem (activity, invoker, persistence, scheduler, etc.) with minimal noise.

For contributors, tests are the first line of code review: they must document intended behaviour and prevent regressions.

Glossary

Activity — a single unit of workflow logic (e.g., WriteLine, If, ForEach, HttpRequest).
Workflow — a graph of activities connected by control flow.
Workflow Definition — a serializable representation of a workflow (JSON or code).
Workflow Instance — a persisted execution of a workflow definition, including state, variables, and journal.
Bookmark — a pause point in a workflow where execution is suspended until an external event resumes it.
Invoker — the core engine component that orchestrates workflow execution, including activity execution, scheduling, and state transitions.
Scheduler — the subsystem that manages background tasks, timers, and resumption of workflows.
Journal — a log of all activity executions and state changes in a workflow instance.
Persistence — the storage mechanism for workflow definitions and instances (e.g., EF Core, MongoDB).
Unit Test — a test that verifies a small, isolated piece of code (such as a function or method) works as expected.
Integration Test — a test that verifies the interaction between multiple components or subsystems works as expected.
Component Test — a test that verifies the behavior of a larger part of the system, often involving persistence and external dependencies.

High-level testing pyramid

Unit tests — single-class logic (activities, converters, expression evaluators, serializers, service providers). Fast; no persistence.
Integration tests — multiple Elsa subsystems together (e.g., invoker + activities + registries). In-process; may deserialize workflow JSON. Use IWorkflowRunner.RunAsync and PopulateRegistriesAsync() when using existing definitions.
Component tests — persisted behaviour, journal/instance store assertions, bookmarks/resumption across lifecycle boundaries. Use AppComponentTest to instantiate and IWorkflowInstanceStore queries for assertions.

Each test layer has distinct goals and clear boundaries — see Which parts of Elsa to test for precise mapping of which aspects belong to which layer.

Quick Start for Contributors

Before you write a test:

✅ Understand what you're testing (see Which parts of Elsa to test)
✅ Choose the right test layer (unit vs integration vs component)
✅ Use existing helpers (don't reinvent - see Test Helpers Reference)

5-Minute Checklist:

Read the relevant section below for your change type:
- Changed activity logic or created a new activity? → See Activities
- Changed workflow execution? → See Workflows execution
Follow steps and code patterns in that section
Run tests locally: dotnet test
Verify no flaky behavior (run 10 times: dotnet test --no-build -- repeat 10)

Characteristics for testing

Activities: First-class pluggable units. Each activity implements execution logic and interacts with the ActivityExecutionContext. More details in Activities.
Workflows: Graphs of activities. A workflow can run synchronously or schedule asynchronous work (bookmarks, timers). When you run a workflow in-process with IWorkflowRunner.RunAsync, the runner will return when synchronous work completes. Some activities set RunAsynchronously causing background scheduling — tests need to take care when asserting. More details in Workflow execution.

Test Project Organization

Tests are organized by module and test type:

test/unit/Elsa.Activities.UnitTests - Activity unit tests
test/unit/Elsa.Expressions.UnitTests - Expression evaluation unit tests
test/unit/Elsa.Workflows.Core.UnitTests - Core workflow unit tests (ActivityExecutionContext extensions, etc.)
test/unit/Elsa.Workflows.Management.UnitTests - Workflow management unit tests
test/integration/Elsa.Workflows.IntegrationTests - Workflow integration tests
test/component/Elsa.Workflows.ComponentTests - End-to-end component tests

Shared test infrastructure:

src/common/Elsa.Testing.Shared - Shared test helpers (ActivityTestFixture, fake strategies, extensions)
src/common/Elsa.Testing.Shared.Integration - Integration test helpers (RunActivityExtensions, PopulateRegistriesAsync)
src/common/Elsa.Testing.Shared.Component - Component test helpers (event handlers, workflow events)

Which parts of Elsa to test, and which test types to use

This section maps Elsa aspects to the exact kinds of tests you should write, with examples and code patterns referencing repository conventions.

Activities

Unit tests:

Test the activity class logic only (no persistence, no scheduler). Cover configuration permutations and boundary inputs.
Use ActivityTestFixture to configure and execute the activity and obtain an ActivityExecutionContext for assertions.
Use fluent methods: ConfigureServices() to add custom services, ConfigureContext() to set up context state
Assert using context.GetActivityOutput()(extension method) for outputs, or context.Get() for variables.

Example (does not set output):

[Fact]
public async Task Should_Set_Variable_Integer()
{
    // Arrange
    const int expected = 42;
    var variable = new Variable<int>("myVar", 0, "myVar");
    var setVariable = new SetVariable<int>(variable, new Input<int>(expected));

    // Act
    var fixture = new ActivityTestFixture(setVariable);
    var context = await fixture.ExecuteAsync();

    // Assert
    var result = context.Get(variable);
    Assert.Equal(expected, result);
}

Example (sets output using fluent configuration):

[Fact]
public async Task Should_Send_Get_Request_And_Handle_Success_Response()
{
    // Arrange
    var expectedUrl = new Uri("https://example.com");
    var sendHttpRequest = new SendHttpRequest
    {
        Url = new Input<Uri?>(expectedUrl),
        Method = new Input<string>("GET")
    };

    // Act
    var fixture = new ActivityTestFixture(sendHttpRequest)
        .WithHttpServices(responseHandler); // HTTP-specific extension
    var context = await fixture.ExecuteAsync();

    // Assert
    var statusCodeOutput = context.GetActivityOutput(_ => sendHttpRequest.StatusCode);
    Assert.Equal(200, statusCodeOutput);
}

Example (checking scheduled activities):

[Fact]
public async Task Should_Schedule_Child_Activity()
{
    // Arrange
    var childActivity = new WriteLine("Hello");
    var parentActivity = new Sequence { Activities = [childActivity] };

    // Act
    var fixture = new ActivityTestFixture(parentActivity);
    var context = await fixture.ExecuteAsync();

    // Assert
    Assert.True(context.HasScheduledActivity(childActivity));
}

Example (checking activity outcomes):

[Fact]
public async Task Should_Return_Multiple_Outcomes()
{
    // Arrange
    var flowFork = new FlowFork
    {
        Branches = new(new[] { "Branch1", "Branch2", "Branch3" })
    };

    // Act
    var context = await new ActivityTestFixture(flowFork).ExecuteAsync();

    // Assert - Check all outcomes
    var outcomes = context.GetOutcomes().ToList();
    Assert.Equal(3, outcomes.Count);
    Assert.Contains("Branch1", outcomes);
    Assert.Contains("Branch2", outcomes);
    Assert.Contains("Branch3", outcomes);
}

[Fact]
public async Task Should_Return_Default_Outcome()
{
    // Arrange
    var flowSwitch = new FlowSwitch();

    // Act
    var context = await new ActivityTestFixture(flowSwitch).ExecuteAsync();

    // Assert - Check single outcome
    Assert.True(context.HasOutcome("Default"));
}

Integration tests:

Place the activity inside a minimal workflow definition and run via IWorkflowRunner.RunAsync. Assert outputs/variables and that the activity integrates correctly with preceding/following activities.
Use WorkflowTestFixture for simplified integration testing with automatic service provider setup and output capture.
If activity creates bookmarks or relies on scheduler semantics, integration tests should resume bookmarks via the engine APIs to validate resumption.

Pattern note: RunAsync returns a RunWorkflowResult (or equivalent) containing the WorkflowInstance and output variables when run to completion. Use returned state for deterministic assertions where possible.

Example (using WorkflowTestFixture - basic):

public class RunJavaScriptTests
{
    private readonly WorkflowTestFixture _fixture;

    public RunJavaScriptTests(ITestOutputHelper testOutputHelper)
    {
        _fixture = new WorkflowTestFixture(testOutputHelper);
    }

    [Fact(DisplayName = "RunJavaScript should execute and return output")]
    public async Task Should_Execute_And_Return_Output()
    {
        // Arrange
        var script = "return 1 + 1;";
        var activity = new RunJavaScript { Script = new(script), Result = new() };

        // Act
        var result = await _fixture.RunActivityAsync(activity);

        // Assert - activity produced expected output
        var output = result.GetActivityOutput<object>(activity);
        Assert.Equal(2, output);
    }

    [Fact(DisplayName = "RunJavaScript should set outcomes")]
    public async Task Should_Set_Outcomes()
    {
        // Arrange
        var script = "setOutcomes(['Branch1', 'Branch2']);";
        var activity = new RunJavaScript { Script = new(script) };

        // Act
        var result = await _fixture.RunActivityAsync(activity);

        // Assert - activity produced expected outcomes
        var outcomes = _fixture.GetOutcomes(result, activity);
        Assert.Contains("Branch1", outcomes);
        Assert.Contains("Branch2", outcomes);
    }

    [Fact(DisplayName = "RunJavaScript should fault on invalid syntax")]
    public async Task Should_Fault_On_Invalid_Syntax()
    {
        // Arrange
        var script = "this is not valid javascript";
        var activity = new RunJavaScript { Script = new(script) };

        // Act
        var result = await _fixture.RunActivityAsync(activity);

        // Assert - activity should be in faulted state
        var status = _fixture.GetActivityStatus(result, activity);
        Assert.Equal(ActivityStatus.Faulted, status);
    }
}

Example (using manual setup with IWorkflowRunner):

[Fact]
public async Task Should_Execute_Workflow()
{
    // Arrange
    var services = new TestApplicationBuilder(testOutputHelper).Build();
    await services.PopulateRegistriesAsync();
    var runner = services.GetRequiredService<IWorkflowRunner>();
    var workflow = Workflow.FromActivity(new WriteLine("Hello"));

    // Act
    var result = await runner.RunAsync(workflow);

    // Assert
    Assert.Equal(WorkflowStatus.Finished, result.WorkflowState.Status);
}

Workflow execution (invoker, middleware, bookmarks)

Unit tests:

Rare: low-level pure helpers in the invoker may have unit tests for edge cases. Most invoker behavior requires integration testing.

Integration tests:

Use IWorkflowRunner.RunAsync with small workflows to test variables propagation, branch logic (If/ForEach/Parallel), expression evaluation, and RunAsynchronously flags.
When a workflow schedules async child work (bookmarks), simulate resumption by calling resume APIs.

Call the workflow runner to execute a workflow object or a loaded definition. Prefer this when asserting logical flow and outputs.

var runner = serviceProvider.GetRequiredService<IWorkflowRunner>();
await serviceProvider.PopulateRegistriesAsync();
var runResult = await runner.RunAsync(workflow);
Assert.Equal(WorkflowStatus.Finished, runResult.WorkflowInstance!.Status);

Component tests (persistence & resumption):

Start a workflow that creates a bookmark. Persisted instance must be found via IWorkflowInstanceStore after the creation point. Simulate host restart by disposing and rebuilding the service provider (keeping the same persistence store) and resume the bookmark to assert resumption completes.

Code pattern to resume a bookmark (integration/component):

// assume instanceId found via RunAsync or correlation id
await workflowTriggerService.ResumeAsync(instanceId, activityId, input, CancellationToken.None);
var resumed = await runner.RunAsync(workflowInstance);
Assert.Equal(WorkflowStatus.Finished, resumed.WorkflowInstance.Status);

Test Helpers Reference (Quick Lookup)

Helper	Purpose	Use When
`TestApplicationBuilder`	Build test service provider	All tests as entry point, except activities unit tests (see below)
`ActivityTestFixture`	Configure and run single activity in isolation	Unit testing activities
`ActivityTestFixture.ConfigureServices`	Fluent API to add services to fixture	Activity unit tests requiring custom services
`ActivityTestFixture.ConfigureContext`	Fluent API to configure execution context before execution	Setting up test-specific context state
`ActivityTestFixture.BuildAsync`	Build context without executing activity	When you need context setup without execution
`ActivityTestFixture.ExecuteAsync`	Execute activity and return context	Standard activity unit test execution
`WorkflowTestFixture`	Configure and run workflows/activities in integration tests	Integration testing workflows and activities
`WorkflowTestFixture.ConfigureElsa`	Fluent API to configure Elsa features	Integration tests requiring custom Elsa configuration
`WorkflowTestFixture.ConfigureServices`	Fluent API to add services to fixture	Integration tests requiring custom services
`WorkflowTestFixture.RunActivityAsync`	Run single activity as workflow	Integration tests for single activities
`WorkflowTestFixture.RunWorkflowAsync`	Run workflow or workflow by definition ID	Integration tests for workflows
`WorkflowTestFixture.CapturingTextWriter`	Capture WriteLine output	Asserting text output in integration tests
`WorkflowTestFixture.GetOutcomes`	Get all outcomes from specific activity	Asserting activity outcomes in integration tests
`WorkflowTestFixture.HasOutcome`	Check if activity produced specific outcome	Asserting single outcome in integration tests
`WorkflowTestFixture.GetActivityStatus`	Get execution status of specific activity	Asserting activity status (Faulted, Completed, etc.)
`WorkflowTestFixture.CreateWorkflowExecutionContextAsync`	Create workflow execution context without running workflow	Testing workflow-level concerns or base context setup
`WorkflowTestFixture.CreateActivityExecutionContextAsync`	Create activity execution context (2 overloads)	Testing activity scheduling/execution or when needing activity context
`WorkflowTestFixture.CreateExpressionExecutionContextAsync`	Create expression execution context (2 overloads)	Testing expression evaluators (JavaScript, Liquid, C#) with variables
`context.GetActivityOutput`	Get output from activity using expression selector	Asserting activity outputs in unit tests
`context.HasScheduledActivity`	Check if activity is scheduled	Verifying scheduling behavior in unit tests
`context.GetOutcomes`	Get all outcomes from activity execution	Asserting multiple outcomes in unit tests
`context.HasOutcome`	Check if activity has specific outcome	Asserting single outcome in unit tests
`IWorkflowRunner.RunAsync`	Execute workflow in-process	Integration / Component tests
`RunActivityExtensions.RunActivityAsync`	Run single activity as workflow	Integration tests for single activities
`PopulateRegistriesAsync`	Register types for JSON deserialization	Loading JSON workflows. Integration tests only
`IWorkflowInstanceStore`	Query persisted instances	Component tests (persistence)
`AsyncWorkflowRunner.RunAndAwaitWorkflowCompletionAsync`	Drive workflow to completion with activity tracking	Complex async scenarios. Component tests only
`FakeActivityExecutionContextSchedulerStrategy`	Fake scheduler for unit tests	Automatically configured in `ActivityTestFixture`
`FakeWorkflowExecutionContextSchedulerStrategy`	Fake workflow scheduler for unit tests	Automatically configured in `ActivityTestFixture`

Scheduler Strategies for Testing

When testing activities in isolation, Elsa provides fake scheduler strategy implementations that bypass the production scheduling logic:

Available Strategies

FakeActivityExecutionContextSchedulerStrategy (source) - Schedules activities immediately within the activity execution context for deterministic testing
FakeWorkflowExecutionContextSchedulerStrategy (source) - Schedules activities immediately at the workflow level for deterministic testing

These strategies are automatically configured when using ActivityTestFixture and ensure that scheduled activities execute synchronously in tests, making assertions deterministic.

Note: You do not need to manually configure these strategies - ActivityTestFixture handles this for you.

Decision helper (what to add — follow in order)

Changed code is a single activity class with no persistence/external calls? → Unit test only.
Change touches multiple activities or workflow logic (If, ForEach, Parallel, Flow activities, etc.)? → Integration test using IWorkflowRunner.RunAsync and a small workflow.
Change touches invoker/scheduler/bookmarks or similar multi-component feature? → Integration test using IWorkflowRunner.RunAsync and a small workflow. If persistence semantics change, add component tests.
Change touches persistence/serializers or requires durable evidence (journal, bookmarks)? → Component tests against IWorkflowInstanceStore.

Rule of thumb:

If it’s about internal logic, write a unit test.
If it’s about collaboration between components, write an integration test.
If it’s about end-to-end feature behavior, write a component test

When in doubt, add the minimal unit tests plus one integration test that reproduces the scenario.

Deterministic patterns to avoid flaky tests

For activity unit tests, prefer returned state from ActivityTestFixture.ExecuteAsync. Always inspect on the returned context — it is deterministic for synchronous workflows.
Resume bookmarks explicitly. Do not wait for external schedulers — call the engine's resume/trigger APIs in your test to continue execution.
For integration tests, locate instances deterministically. Use an instance id returned by RunAsync or attach a CorrelationId test variable and query IWorkflowInstanceStore.FindByCorrelationIdAsync(...). Avoid using "latest" queries.

WorkflowTestFixture Helper Methods

When using WorkflowTestFixture for integration tests, use these helper methods to assert on activity behavior:

Asserting Activity Outputs

Use result.GetActivityOutput<T>(activity) to retrieve the output value from an activity:

var result = await _fixture.RunActivityAsync(activity);
var output = result.GetActivityOutput<object>(activity);
Assert.Equal(expectedValue, output);

Asserting Activity Outcomes

Use _fixture.GetOutcomes(result, activity) to retrieve all outcomes produced by an activity:

var result = await _fixture.RunActivityAsync(activity);
var outcomes = _fixture.GetOutcomes(result, activity);
Assert.Contains("ExpectedOutcome", outcomes);

Or use _fixture.HasOutcome(result, activity, outcome) to check for a specific outcome:

var result = await _fixture.RunActivityAsync(activity);
Assert.True(_fixture.HasOutcome(result, activity, "Success"));

Asserting Activity Status

Use _fixture.GetActivityStatus(result, activity) to check the execution status of an activity:

var result = await _fixture.RunActivityAsync(activity);
var status = _fixture.GetActivityStatus(result, activity);
Assert.Equal(ActivityStatus.Faulted, status);

Available activity statuses:

ActivityStatus.Pending - Activity is pending execution
ActivityStatus.Running - Activity is currently running
ActivityStatus.Completed - Activity completed successfully
ActivityStatus.Canceled - Activity was canceled
ActivityStatus.Faulted - Activity encountered an error

Creating Execution Contexts for Testing

WorkflowTestFixture provides layered methods for creating execution contexts at different levels, giving you fine-grained control over test setup:

Creating a Workflow Execution Context

Use CreateWorkflowExecutionContextAsync to create a minimal workflow execution context without running the workflow:

var context = await _fixture.CreateWorkflowExecutionContextAsync(variables: new[]
{
    new Variable<int>("Counter", 0)
});

Creating an Activity Execution Context

Use CreateActivityExecutionContextAsync to create an activity execution context. Two overloads available:

Without existing workflow context (creates one automatically):

var activityContext = await _fixture.CreateActivityExecutionContextAsync(
    activity: myActivity,
    variables: new[] { new Variable<string>("MyVar", "value") }
);

With existing workflow context:

var workflowContext = await _fixture.CreateWorkflowExecutionContextAsync();
var activityContext = await _fixture.CreateActivityExecutionContextAsync(
    workflowContext,
    activity: myActivity
);

Creating an Expression Execution Context

Use CreateExpressionExecutionContextAsync to create a context for testing expression evaluation (e.g., JavaScript, Liquid). Variables are properly registered and accessible via dynamic accessors. Two overloads available:

Without existing activity context (creates one automatically):

var expressionContext = await _fixture.CreateExpressionExecutionContextAsync(new[]
{
    new Variable<string>("MyVariable", "test value")
});

// Variables are accessible via dynamic accessors in expressions
// e.g., getMyVariable() and setMyVariable(value) in JavaScript

With existing activity context:

var activityContext = await _fixture.CreateActivityExecutionContextAsync();
var expressionContext = await _fixture.CreateExpressionExecutionContextAsync(
    activityContext,
    variables: new[] { new Variable<int>("Count", 42) }
);

Example: Testing JavaScript Expression Evaluation

[Fact]
public async Task Dynamic_Variable_Accessors_Should_Work()
{
    // Arrange
    var script = @"
        setMyVariable('updated value');
        return getMyVariable();
    ";
    var context = await _fixture.CreateExpressionExecutionContextAsync(new[]
    {
        new Variable<string>("MyVariable", "initial value")
    });

    // Act
    var evaluator = _fixture.Services.GetRequiredService<IJavaScriptEvaluator>();
    var result = await evaluator.EvaluateAsync(script, typeof(string), context);

    // Assert
    Assert.Equal("updated value", result);
}

When to use each method:

Use CreateWorkflowExecutionContextAsync when testing workflow-level concerns or when you need a base context for further customization
Use CreateActivityExecutionContextAsync when testing activity scheduling, execution, or when you need access to activity-specific context
Use CreateExpressionExecutionContextAsync when testing expression evaluators (JavaScript, Liquid, C#) or when you need variables to be accessible in expressions

Failure testing (faults & incidents)

Integration test faulted activities: Use _fixture.GetActivityStatus(result, activity) to assert that a specific activity faulted, rather than checking workflow-level status.
Integration test faulted workflows: build a workflow that throws and run via RunAsync — assert WorkflowInstance.Status == Faulted on the returned state or via IWorkflowInstanceStore.
Component tests for recovery/resume: persist a faulted instance (or cause a host restart scenario), run your recovery logic, and assert the final state.

Practical test recipes & snippets

Unit test (activity) — pattern

[Fact]
public async Task MyActivity_Test()
{
    var activity = new ActivityToTest();

    // Act
    var fixture = new ActivityTestFixture(activity);
    var context = await fixture.ExecuteAsync();

    // assert behavior of activity in isolation
}

Integration test — pattern using `WorkflowTestFixture`

Recommended approach for activity integration tests:

public class MyActivityTests
{
    private readonly WorkflowTestFixture _fixture;

    public MyActivityTests(ITestOutputHelper testOutputHelper)
    {
        _fixture = new WorkflowTestFixture(testOutputHelper);
    }

    [Fact]
    public async Task Activity_Completes_Successfully()
    {
        // Arrange
        var activity = new MyActivity { Input = new("test") };

        // Act
        var result = await _fixture.RunActivityAsync(activity);

        // Assert
        Assert.Equal(WorkflowStatus.Finished, result.WorkflowState.Status);
    }
}

Integration test — pattern using `IWorkflowRunner.RunAsync`

Alternative approach with manual setup (use when you need more control):

[Fact]
public async Task Workflow_With_MyActivity_Completes()
{
    var sp = new TestApplicationBuilder(testOutput).Build();
    await sp.PopulateRegistriesAsync();

    var runner = sp.GetRequiredService<IWorkflowRunner>();
    var workflow = new MyWorkflowDefinition();

    var result = await runner.RunAsync(workflow);

    Assert.Equal(WorkflowStatus.Finished, result.WorkflowInstance!.Status);
}

Component test

[Fact]
public async Task Workflow_Persists_Instance_And_Journal()
{
    var sp = new TestApplicationBuilder(testOutput)
        .Build();

    var runner = sp.GetRequiredService<AsyncWorkflowRunner>();
    var result = await runner.RunAndAwaitWorkflowCompletionAsync(
        WorkflowDefinitionHandle.ByDefinitionId(someDefinitionId, VersionOptions.Published)
    );
    result.WorkflowExecutionContext.Status.Should().Be(WorkflowStatus.Finished);
}

Component test with async workflow execution

For testing workflows that complete asynchronously (e.g., with timers, external triggers), use AsyncWorkflowRunner:

[Fact]
public async Task Workflow_Completes_Asynchronously()
{
    var sp = new TestApplicationBuilder(testOutput).Build();
    var runner = sp.GetRequiredService<AsyncWorkflowRunner>();

    var result = await runner.RunAndAwaitWorkflowCompletionAsync(
        WorkflowDefinitionHandle.ByDefinitionId(workflowId, VersionOptions.Published)
    );

    result.WorkflowExecutionContext.Status.Should().Be(WorkflowStatus.Finished);
    result.ActivityExecutionRecords.Should().HaveCount(expectedCount);
}

AsyncWorkflowRunner tracks activity execution records and awaits workflow completion signals, making it ideal for testing asynchronous workflow behavior deterministically.

FAQ (quick pointers)

Q: How do I import workflow definitions in tests and where do I put them?

A: For JSON-defined workflows use the repo's test integration helpers (PopulateRegistriesAsync() or the test registration helpers in test/common). See integration test examples in the test tree. Leave the definitions next to the tests that use them.

Q: Which helper should I use to run a workflow?

A: Prefer IWorkflowRunner.RunAsync for in-process deterministic runs. For activities use ActivityTestFixture.

Q: How do I check persisted journal entries?

A: Query IWorkflowInstanceStore and inspect the persisted journal on the instance. Use deterministic instance id or correlation id to locate the exact instance.

Q: Do I need a new helper to wait for workflow completion?

A: No. The repo provides RunAsync for integration tests and ActivityTestFixture for activity unit tests, as well as integration helpers that cover all necessary scenarios. For async workflows in component tests, use AsyncWorkflowRunner.

Appendix — examples in the repository (where to look)

Search the test/ tree for examples that follow the above patterns:

Unit test activity examples: test/unit/Elsa.Activities.UnitTests (look for ActivityTestFixture usage)
Integration workflow examples: test/integration/Elsa.*.IntegrationTests (look for PopulateRegistriesAsync() and IWorkflowRunner.RunAsync usage)
Component scenarios exercising persistence: test/component/Elsa.Workflows.ComponentTests (look for AsyncWorkflowRunner and IWorkflowInstanceStore assertions)