Simulating Stateful Behavior for Testing#

Most web services tend to have some state, which changes as you and others interact with it. So it's pretty useful to be able to simulate this when you've swapped a real service for a test double.

Scenarios#

WireMock supports state via the notion of scenarios. A scenario is essentially a state machine whose states can be arbitrarily assigned. Its starting state is always Scenario.STARTED. Stub mappings can be configured to match on scenario state, such that stub A can be returned initially, then stub B once the next scenario state has been triggered.

For example, suppose we're writing a to-do list application consisting of a rich client of some kind talking to a REST service. We want to test that our UI can read the to-do list, add an item and refresh itself, showing the updated list.

In Java this could be set up like this:

@Test
public void toDoListScenario() {
    stubFor(get(urlEqualTo("/todo/items")).inScenario("To do list")
            .whenScenarioStateIs(STARTED)
            .willReturn(aResponse()
                    .withBody("<items>" +
                            "   <item>Buy milk</item>" +
                            "</items>")));

    stubFor(post(urlEqualTo("/todo/items")).inScenario("To do list")
            .whenScenarioStateIs(STARTED)
            .withRequestBody(containing("Cancel newspaper subscription"))
            .willReturn(aResponse().withStatus(201))
            .willSetStateTo("Cancel newspaper item added"));

    stubFor(get(urlEqualTo("/todo/items")).inScenario("To do list")
            .whenScenarioStateIs("Cancel newspaper item added")
            .willReturn(aResponse()
                    .withBody("<items>" +
                            "   <item>Buy milk</item>" +
                            "   <item>Cancel newspaper subscription</item>" +
                            "</items>")));

    WireMockResponse response = testClient.get("/todo/items");
    assertThat(response.content(), containsString("Buy milk"));
    assertThat(response.content(), not(containsString("Cancel newspaper subscription")));

    response = testClient.postWithBody("/todo/items", "Cancel newspaper subscription", "text/plain", "UTF-8");
    assertThat(response.statusCode(), is(201));

    response = testClient.get("/todo/items");
    assertThat(response.content(), containsString("Buy milk"));
    assertThat(response.content(), containsString("Cancel newspaper subscription"));
}

The JSON equivalent for the above three stubs is:

{
    "mappings": [
        {
            "scenarioName": "To do list",
            "requiredScenarioState": "Started",
            "request": {
                "method": "GET",
                "url": "/todo/items"
            },
            "response": {
                "status": 200,
                "body": "<items><item>Buy milk</item></items>"
            }
        },
        {
            "scenarioName": "To do list",
            "requiredScenarioState": "Started",
            "newScenarioState": "Cancel newspaper item added",
            "request": {
                "method": "POST",
                "url": "/todo/items",
                "bodyPatterns": [
                    { "contains": "Cancel newspaper subscription" }
                ]
            },
            "response": {
                "status": 201
            }
        },
        {
            "scenarioName": "To do list",
            "requiredScenarioState": "Cancel newspaper item added",
            "request": {
                "method": "GET",
                "url": "/todo/items"
            },
            "response": {
                "status": 200,
                "body": "<items><item>Buy milk</item><item>Cancel newspaper subscription</item></items>"
            }
        }
    ]
}

Getting scenario state#

The names, current state and possible states of all scenarios can be fetched.

Java:

List<Scenario> allScenarios = getAllScenarios();

JSON:

GET /__admin/scenarios
{
  "scenarios" : [ {
    "id" : "my_scenario",
    "name" : "my_scenario",
    "state" : "Started",
    "possibleStates" : [ "Started", "state_2", "state_3" ]
  } ]
}

Resetting scenarios#

The state of all configured scenarios can be reset back to Scenario.START either by calling

Java:

WireMock.resetAllScenarios()

To do the equivalent via the HTTP API, send an empty POST request to /__admin/scenarios/reset.

Resetting a single scenario#

You can reset the state of an individual scenario.

Java:

WireMock.resetScenario("my_scenario");

The do the equivalent via the HTTP API, send an empty PUT to /__admin/scenarios/my_scenario/state.

Setting the state of an individual scenario#

You can also set the state of an individual scenario to a specific value.

Java:

WireMock.setScenarioState("my_scenario", "state_2");

HTTP:

PUT /__admin/scenarios/my_scenario/state
{
    "state": "state_2"
}