This document discusses using Mountebank to test components in isolation and integration. It provides an overview of Mountebank and its key concepts: - Imposters represent services and contain responses. They are associated with a port and protocol. - Predicates determine if a request matches an imposter's configuration. Common predicates check request properties like method or path. - Proxies record and replay real service responses to test interactions without external dependencies. The document includes examples of creating imposters and proxies to represent services, as well as using predicates to match specific requests. It outlines how Mountebank can stub unreliable or non-existent dependencies to enable testing isolated components or integrated systems.

1. MOUNTEBANK AND
YOU
Nagesh Kumar
nkumar@thoughtworks.com
1

2. AGENDA
Integration Testing
Isolation Testing
Real Problem
Mountebank
Quick Watch
Whom to Catch
2

3. Test multiple components at the same time
No GUI
No faking/mocking/stubbing/etc
Need Real things to Integrate With
Real Services must be reliable and need to be fast
THE CLASSICAL VIEW OF INTEGRATION TESTING
3

4. THE CLASSICAL VIEW OF ISOLATION TESTING
4
Test as many real components at the same time
Stub out the unreliable Real Dependency
Stub out the non-existing Real Dependency
Testing our code while isolating it from the naughty Real
Dependency

5. YOU CAN’T ALWAYS FIX THE REAL PROBLEM (SAD, BUT TRUE)
5
Real Things being maintained/developed by other teams
Poor testing environment (Hardware, Data, Other)
Fixing the Real Thing is more costly than enduring it
Client won’t pay us to fix the Real Things

6. WHAT IS MOUNTEBANK?
“mountebank is the
first tool to provide
cross-platform, multi-
protocol test doubles
over the wire.”
- mountebank
6
http://www.mbtest.org/

7. WHY MOUNTEBANK?
Proprietary
Lacked platform support
Lacked protocol support
Not extensible
Slow
Hard to run during unit test cycle
Managed through a special IDE
7
Existing tools were:

8. WHAT CAN IT DO FOR ME?
Record live requests and responses to replay later
Imitate a response from scratch
Respond to specific requests via predicates
Track any requests that come its way
8

9. AN OVERVIEW OF MOUNTEBANK IN ACTION
System
Under Test
Tests
Mountebank
Stub

10. WHAT DO I NEED TO KNOW IN MB?
Imposters
Predicates
Proxies
Injection
Behaviors
10

11. WHAT ARE IMPOSTERS?
The imposter is the
most integral part of
mountebank. An
imposter is associated
with a port number
and a protocol. It
contains within itself
the response we want
to return, and other
related information.
11
http://www.mbtest.org/docs/api/stubs

12. ANATOMY OF AN IMPOSTER
POST /imposters HTTP/1.1
Host: localhost:2525
Accept: application/json
Content-Type: application/json
{
"port": 4545,
"protocol": “http",
"stubs": [
{
"responses": [
{
"is": {
"statusCode": 200, (Will default to 200 if not provided)
“headers": {
“Content-Type": “text/plain“
},
"body": “Hello world!”
}
}
]
}
]
}
12

13. ANOTHER IMPOSTER EXAMPLE
POST /imposters HTTP/1.1
Host: localhost:2525
Accept: application/json
Content-Type: application/json
{
"port": 4546,
"protocol": "http",
"stubs": [
{
"responses": [
{
"is": {
"statusCode": 201,
“headers": {
“Content-Type": “text/plain“
},
"body": “Created!”
}
},
{
"is": {
"statusCode": 400,
“headers": {
“Content-Type": “text/plain“
},
"body": “ERROR: Already Exists!”
}
}
]
}
]
}
13

14. WHAT IS A PREDICATE?
The predicate is the
part of an imposter
which determines if a
request should be
responded to by said
imposter.
14
http://www.mbtest.org/docs/api/predicates

15. TYPES OF PREDICATES
Equals
Deep Equals
Contains
Starts/EndsWith
Matches
Exists
Not/And/Or
Inject
http://www.mbtest.org/docs/api/predicates
15

16. WHAT CAN A PREDICATE OPERATE ON?
That depends on the
protocol you’re using!
For example, Http
allows you to use
predicates on:
- Method Type
- Query Path
- Request Body
- And More!
16
http://www.mbtest.org/docs/protocols/http

17. PREDICATE EXAMPLE
{
"port": 4551,
"protocol": "http",
"stubs": [
{
"responses": [
{
"is": {
"statusCode": 201,
"headers": {
"Content-Type": "text/plain"
},
"body": "You posted to me!"
}
}
],
"predicates": [
{
"equals": {
"method": "POST"
}
}
]
}
]
}
17

18. OR EXAMPLE
{
"port": 4552,
"protocol": "http",
"stubs": [
{
"responses": [
{
"is": {
"statusCode": 201,
"headers": {
"Content-Type": "text/plain"
},
"body": "You posted to me!"
}
}
],
"predicates": [
{
"or": [
{
"equals": {
"method": "POST"
}
},
{
"equals": {
"method": "PUT"
}
}
]
}
]
}
]
}
18

19. WHAT IS A PROXY?
The proxy is a special
imposter which allows
us to get between our
application and a
service it
communicates with. It
records each request,
forwards it to the
service, and records
the response from that
service.
19
http://www.mbtest.org/docs/api/proxies

20. BUT WHAT DO I DO WITH IT?
Record responses that would be difficult (if not impossible)
to write by hand
Look at requests to see what distinguishes them from each
other
20

21. PROXY EXAMPLE
{
"port": 4560,
"protocol": "http",
"name": "duckduckgo",
"stubs": [
{
"responses": [
{
"proxy": {
"to": "http://api.duckduckgo.com/",
"mode": "proxyOnce",
"predicateGenerators": [
{
"matches": {
"method": true,
"path": true,
"query": true
}
}
]
}
}
]
}
]
}
21

22. Direct all Suggestions to Brandon
(bbyars@thoughtworks.com)
THANK YOU