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Resilient Services with Wiremock Effective REST tests using Wiremock and Spock

https://flic.kr/p/orejhX

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How does your system handle failures?

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Everybody tests the happy path…

https://flic.kr/p/9MHEme

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Happy Path Tests

HTTP/1.1 200 OK

{“publicId":"42634558","data":"foo"}

GET http://service/resource/12

Client Service

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But what about the not-so-happy path?

https://flic.kr/p/CSnr1

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Enter Wiremock• Stub and Mock framework

for testing HTTP(s) traffic

• Features include

• Request verification,

• record, playback,

• fault injection,

• unit test and stand alone

Client Unit Test

EmbeddedWiremock

Client Standalone Wiremock

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How does it work?

Client Wiremock

Request Mapping

Response Data

$ curl -H ‘Accept: application/json’ http://localhost:8080/sample/

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How does it work?

Client Wiremock

Request Mapping

Response Data

• Starts embedded Jetty Server

• Acts as a proxy to the actual service

• Is used by the client transparently

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How does it work?

Client Wiremock

Request Mapping

Response Data

"request" : { "url" : "/sample/", "method" : "GET", } } }, "response" : { "status" : 200, "bodyFileName" : "body.json", "headers" : { "Content-Type" : “application/json" … } }

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How does it work?

Client Wiremock

Request Mapping

Response Data

body.json: [{"publicId":"...","data":"..."}, {"publicId":"...","data":"..."}]

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Creating a Wiremock Unittest

Prepare Stub

Configure Wiremock

Consume REST service

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Creating a Wiremock Unittest

Prepare Stub

Configure Wiremock

Consume REST service

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Creating a Wiremock Unittest

Prepare Stub

Configure Wiremock

Consume REST service

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Creating a Wiremock Unittest

Prepare Stub

Configure Wiremock

Consume REST service

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Creating a Wiremock Unittest

Prepare Stub

Configure Wiremock

Consume REST service

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…but what about failures?

HTTP/1.1 503 Service Unavailable

Client Service

GET http://service/resource/12

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Testing Failures

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…but what about bad responses?

Client Service

HTTP/1.1 200 OK Content-Type: application/json;charset=UTF-8

[300 MB of random garbage]

GET http://service/resource/12

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Testing Unexpected Behavior

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…but what about timeouts?

java.net.SocketTimeoutException: Read timed out

Client Service

GET http://service/resource/12

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Testing the circuit breaker

Record and Playback

https://flic.kr/p/nRXLqh

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Record and Playback

Run requests

Start Wiremock in record mode

Start Wiremock in playback mode

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Record and Playback

Demo

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Summary• Resilience can be tested

• Do not rely on happy paths and mocks only

• Use stubs and verify in unit tests

• Use record and playback for external services

• Make sure not to be the developer responsible for a downtime during the busy-business-time :D

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Links

http://wiremock.org/

https://github.com/koenighotze/wiremock-tryout/

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THANK YOU!<david.schmitz@senacor.com>

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BACKUP

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Testing a ClientClient Unit Test

EmbeddedWiremock