Reproducible component tests using docker

Reproducible component tests for
microservices using Docker
Pavel Rabetski

Component tests
● Verify behaviour of a component
● Cheaper to maintain than system tests
● Easier to locate problems compared to system tests

Monolithic app vs Micro Services
Monolithic app
MS
1
MS
3
MS
2
MS
4
● same lifecycle
● same runtime/environment
● component is a “grey box”
● different lifecycle
● different runtime/environment
● component is a “black box”

Component tests
Test
script
MS
Test env

Component tests
S0 S1T1:
S0 S2T2:
S0 S3T3:
Test script

Component tests: tests in sequence
S0 S1T1:
S1 ?T2:

Component tests: repeat same test
S0 S3T3:
S3 ?T3:

Approach 1: cleanup/reset state
S0 S1T1:
S1 S0T1 cleanup:
S0 S2T2:
S2 S0T2 cleanup:
Extra development effort:
keep track of changes and add
cleanup code
Not always possible: e.g.
deleting an entity just marks
delete property = true

Approach 2: separate contexts
Sx SnTn:
UserId=n
S0 S1T1:
UserId=1
Extra development effort:
keep track of the unique
context
Not always possible: if we
have a global resource or
complex pre-generated data
S1 S2T2:
UserId=2

Alternative approach: recreate test environment
Test
script
Less development effort: no
need to separate contexts or
clean up after test
No constraints from previous
methods: possible with global
resource or pre-generated data
MS
Test env
MS
Test env
MS
Test env

Monolithic app

Monolithic app
MS

pavradev/dockerbay
Apache 2.0
It is Java library for component testing
It does orchestrate docker environment
It uses JUnit and Docker Java Client

Example: Hotel booking web app
webapp
db
service webapp
db service

Maven dependency
<dependency>
<groupId>com.github.pavradev</groupId>
<artifactId>dockerbay</artifactId>
<version>${dockerbay.version}</version>
<scope>test</scope>
</dependency>

Configuring dockerbay: JUnit Rule
@Rule
public DockerRule dockerRule = DockerRule.getDefault()
.addContainer(postgresContainer)
.addContainer(reviewsMockContainer)
.addContainer(webappContainer);

Configuring dockerbay: db container
private ContainerConfig postgresContainer = ContainerConfig.builder()
.withImage("postgres:9")
.withName("postgres")
.waitForLogEntry("database system is ready to accept connections")
.build();

Configuring dockerbay: webapp container
private ContainerConfig webapp = ContainerConfig.builder()
.withImage("demo/webapp")
.withName("webapp")
.waitForUrl("/api/hotels")
.withExposedTcpPort(8082)
.build();

Configuring dockerbay: service container
private ContainerConfig reviewsMockContainer = ContainerConfig.builder()
.withImage("ekino/wiremock:2.1.11")
.withName("reviews-mock")
.withExposedTcpPort(8083)
.withCmd(Arrays.asList("--port", "8083", "--verbose"))
.build();

Add tests
public class WebappCT {
@Test
public void shouldGetHotelWithReviews() {
...
}
@Test
public void shouldUpdateHotel() {
...
}
@Test
public void shouldDeleteHotel() {
...
}
}

Add tests
@Test
public void shouldUpdateHotel() {
//create dummy hotel
reqSpec.contentType(ContentType.JSON)
.body("{"name":"Dummy hotel","address":"Dummy address","zip":"4001"}")
.post("/api/hotels");
//update dummy hotel address
.body("{"address":"Updated address","zip":"4004"}")
.put("/api/hotels/1");
//validate address updated
reqSpec.get("/api/hotels/1")
.then()
.assertThat()
.body("address", equalTo("Updated address"));
}

Add tests
@Test
public void shouldGetHotelWithReviews() {
//create dummy hotel
.body("{"name":"Dummy hotel","address":"Dummy address","zip":"4001"}")
.post("/api/hotels");
//mock GET request for hotel reviews
reviewsMock.register(get(urlEqualTo("/api/reviews?hotelId=1"))
.willReturn(aResponse()
.withStatus(200)
.withHeader("Content-Type", "application/json")
.withBody("[...]")));
//validate dummy hotel returned with reviews
reqSpec.get("/api/hotels/1")
.then().assertThat()
.statusCode(200)
.and().body("name", equalTo("Dummy hotel"))
.and().body("reviews.size()", equalTo(1));
}

Execute
pull images
DOCKER_HOST
WM

Execute
pull images
create custom network
DOCKER_HOST
WM
{id}

Execute
pull images
create and start containers
DOCKER_HOST
WM
{id}
webapp
db service
{id}-webapp {id}-db {id}-service

Execute
pull images
execute test
DOCKER_HOST
WM
{id}
webapp
db service
{id}-webapp {id}-db {id}-service

Execute
pull images
stop and remove containers
execute test
DOCKER_HOST
WM
{id}

Execute
pull images
stop and remove containers
execute test
remove custom network
DOCKER_HOST
WM

Parallelization
T1
T2
T3
Test script

Parallelization
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-failsafe-plugin</artifactId>
<configuration>
<parallel>all</parallel>
<threadCount>3</threadCount>
<perCoreThreadCount>false</perCoreThreadCount>
</configuration>
</plugin>

Reproducible component tests using docker

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