Guessing this is not possible?

MassTransitAPIEndPointTest.cs

[Fact]
public async Task Get_GetDefaultEndPoint_ReturnsOk()
{
    // Arrange
    var harness = new InMemoryTestHarness();
    var consumerHarness = harness.Consumer<MyMessageConsumer>();

    await harness.Start();
    try
    {
        // Act
        
        // /api/default -> emits a MyMessage onto the Bus
        var apiResults = await _client.GetAsync("/api/default");
        var apiResponse = await apiResults.Content.ReadAsStringAsync();

        // Assert
        apiResults.StatusCode.Should().Be(HttpStatusCode.OK);
        apiResponse.Should().Be("API1");
        
        consumerHarness.Consumed.Select<MyMessage>().Any().Should().BeTrue();
    }
    finally
    {
        await harness.Stop();
    }
}