Workflow Testing

Workflow Unit Testing with testRender

Write unit tests for individual render passes using testRender and RenderTester. This API fakes all children and workers, letting you test render logic in isolation.

When to Use

• Testing a single render pass in isolation
• Verifying renderings match expected UI models
• Testing state transitions from event handlers
• Testing output emissions
• Verifying props passed to child workflows
• Verifying worker expectations

For multi-step flows or async behavior, use renderForTest / WorkflowTurbine instead (see the workflow-integration-testing skill).

Test File Structure

import com.squareup.workflow1.WorkflowOutput
import com.squareup.workflow1.testing.expectWorker
import com.squareup.workflow1.testing.expectWorkflow
import com.squareup.workflow1.testing.testRender
import kotlin.test.Test
import kotlin.test.assertEquals
import kotlin.test.assertNull

class MyWorkflowTest {

  private val workflow = MyWorkflow()

  @Test fun `renders initial state correctly`() {
    workflow.testRender(
      props = MyProps("test"),
      initialState = MyState.Initial
    )
      .render { rendering ->
        assertEquals("test", rendering.title)
        assertEquals(false, rendering.isLoading)
      }
  }
}

Core API

Starting a Test

// StatefulWorkflow — provide props and state
workflow.testRender(props = myProps, initialState = myState)

// StatefulWorkflow — use workflow's initialState method (null snapshot)
workflow.testRender(props = myProps)

// StatelessWorkflow — props only
workflow.testRender(props = myProps)

Rendering and Asserting

workflow.testRender(props, state)
  .render { rendering ->
    // Assert on rendering properties
    assertEquals("Hello", rendering.title)
    assertTrue(rendering.isLoading)

    // Optionally trigger an event handler (at most one per test)
    rendering.onButtonClicked()
  }

Verifying Actions

After triggering an event handler or receiving a child/worker output, verify the action:

// Option 1: Verify the action identity (for sealed class / enum actions)
.verifyAction { action ->
  assertEquals(MyAction.LoadData, action)
}

// Option 2: Verify the action result (for inline / anonymous actions)
.verifyActionResult { newState, output ->
  assertEquals(MyState.Loading, newState)
  assertNull(output) // no output emitted
}

output is WorkflowOutput<OutputT>? — use output?.value to access the actual value, or check assertNull(output) when no output is expected.

Testing Patterns

State Transitions

@Test fun `button click transitions to loading`() {
  workflow.testRender(
    props = MyProps("test"),
    initialState = MyState.Initial
  )
    .render { rendering ->
      rendering.onLoadClicked()
    }
    .verifyActionResult { newState, output ->
      assertEquals(MyState.Loading, newState)
      assertNull(output)
    }
}

Output Emissions

@Test fun `complete button emits finished output`() {
  workflow.testRender(
    props = MyProps("test"),
    initialState = MyState.Done("result")
  )
    .render { rendering ->
      rendering.onCompleteClicked()
    }
    .verifyActionResult { newState, output ->
      assertEquals(MyOutput.Finished("result"), output?.value)
    }
}

No Action Triggered

@Test fun `renders loading state without triggering action`() {
  workflow.testRender(
    props = MyProps("test"),
    initialState = MyState.Loading
  )
    .render { rendering ->
      // Just assert, don't trigger any event handler
      assertTrue(rendering.isLoading)
      assertEquals("Loading...", rendering.message)
    }
}

Expecting Child Workflows

All child workflows rendered by the workflow-under-test must be faked via providing expectations:

@Test fun `renders child workflow with correct props`() {
  workflow.testRender(props = MyProps("123"), initialState = MyState.ShowChild)
    .expectWorkflow(
      workflowType = ChildWorkflow::class,
      rendering = ChildScreen("faked"),
      key = "",  // default key, omit if not using keys
      assertProps = { props ->
        assertEquals("123", props.itemId)
      }
    )
    .render { rendering ->
      assertEquals("faked", rendering.childContent)
    }
}

Child Workflow Emitting Output

@Test fun `handles child workflow output`() {
  workflow.testRender(props = MyProps("123"), initialState = MyState.ShowChild)
    .expectWorkflow(
      workflowType = ChildWorkflow::class,
      rendering = ChildScreen("faked"),
      output = WorkflowOutput(ChildOutput.Done("result"))
    )
    .render { rendering ->
      // Don't trigger any event handler — child is emitting output
    }
    .verifyActionResult { newState, output ->
      assertEquals(MyState.Complete("result"), newState)
    }
}

Faking Workers

Workers are optionally expected by default. Use requireExplicitWorkerExpectations() to make all workers required.

By Worker Type (KType)

import kotlin.reflect.typeOf

workflow.testRender(props, state)
  .expectWorker(
    workerType = typeOf<Worker<MyData>>(),
    key = "fetchData"
  )
  .render { ... }

By Worker Class (KClass)

workflow.testRender(props, state)
  .expectWorker(
    workerClass = MyCustomWorker::class,
    key = "fetch"
  )
  .render { ... }

By Output Type

workflow.testRender(props, state)
  .expectWorkerOutputting(
    outputType = typeOf<MyData>(),
    key = "fetchData"
  )
  .render { ... }

Worker Emitting Output

workflow.testRender(props, state)
  .expectWorker(
    workerType = typeOf<Worker<MyData>>(),
    key = "fetchData",
    output = WorkflowOutput(MyData("result"))
  )
  .render { rendering ->
    // Don't trigger event handlers — worker is emitting output
  }
  .verifyActionResult { newState, output ->
    assertEquals(MyState.Loaded("result"), newState)
  }

Side Effects

workflow.testRender(props, state)
  .expectSideEffect(key = "analytics")
  .render { ... }

Side effects are optionally expected by default. Use requireExplicitSideEffectExpectations() to require all side effects be expected.

Chaining Render Passes

Test multiple sequential renders without the overhead of a full runtime:

@Test fun `multi-step flow`() {
  workflow.testRender(props = MyProps("test"), initialState = MyState.Initial)
    .render { rendering ->
      rendering.onLoadClicked()
    }
    .verifyActionResult { newState, _ ->
      assertEquals(MyState.Loading, newState)
    }
    // Continue with the new state from the previous action
    .testNextRender()
    .expectWorker(workerType = typeOf<Worker<Data>>(), key = "fetch")
    .render { rendering ->
      assertTrue(rendering.isLoading)
    }
}

With New Props

.testNextRenderWithProps(MyProps("updated"))
  .render { rendering ->
    assertEquals("updated", rendering.title)
  }

Note: testNextRenderWithProps will call onPropsChanged if the workflow overrides it.

Best Practices

1. Test one behavior per test — each test should verify one event handler or one render state
2. Use verifyActionResult for inline/anonymous actions (most common)
3. Use verifyAction for sealed class or enum actions where you test the action type
4. Use requireExplicitWorkerExpectations() when you need to verify no unexpected workers run
5. Descriptive test names with backticks: `button click transitions to loading`
6. Only trigger one event per render — triggering an event AND having a child/worker emit output in the same render is an error

Required Imports

// Core testing API
import com.squareup.workflow1.testing.testRender

// Expectations
import com.squareup.workflow1.testing.expectWorkflow
import com.squareup.workflow1.testing.expectWorker
import com.squareup.workflow1.testing.expectWorkerOutputting
import com.squareup.workflow1.testing.expectSideEffect

// Output wrapper
import com.squareup.workflow1.WorkflowOutput

// For worker type matching
import kotlin.reflect.typeOf
import com.squareup.workflow1.Worker

// Assertions
import kotlin.test.Test
import kotlin.test.assertEquals
import kotlin.test.assertNull
import kotlin.test.assertTrue

Deprecated APIs — Do NOT Use

• launchForTestingFromStartWith — replaced by renderForTest
• launchForTestingWith — replaced by renderForTest
• WorkflowTestRuntime — replaced by WorkflowTurbine

These are deprecated integration test APIs. For integration testing, use the workflow-integration-testing skill instead.

Documentation

• RenderTester API: https://square.github.io/workflow/kotlin/api/htmlMultiModule/workflow-testing/com.squareup.workflow1.testing/-render-tester/index.html
• testRender: https://square.github.io/workflow/kotlin/api/htmlMultiModule/workflow-testing/com.squareup.workflow1.testing/test-render.html
• expectWorkflow: https://square.github.io/workflow/kotlin/api/htmlMultiModule/workflow-testing/com.squareup.workflow1.testing/expect-workflow.html
• expectWorker: https://square.github.io/workflow/kotlin/api/htmlMultiModule/workflow-testing/com.squareup.workflow1.testing/expect-worker.html

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