Proxies

Proxies are one of the most powerful features of mountebank, rivaled only by the mighty injection. Proxies support record/replay behavior to easily capture a rich set of test data for your test scenarios. Each proxy definition allows you to define the fields which should be included in newly created predicates.

proxy response types take the following parameters:

Parameter	Default	Type	Description
`to`	required	A URL without the path (e.g. http://someserver:3000 or tcp://someserver:3000)	Defines the origin server that the request should proxy to.
`predicateGenerators`	`[]`	array	An array of objects that defines how the predicates for new stubs are created. Each object in the array defines the fields to generate predicates from. See below for examples.
`mode`	`proxyOnce`	string, one of `proxyOnce`, `proxyAlways` or `proxyTransparent`.	Defines the replay behavior of the proxy. The default `proxyOnce` mode doesn't require you to explicitly do anything to replay the proxied responses. The `proxyAlways` mode requires you to run the `mb replay` command (or equivalent) to switch from record mode to replay mode, but allows a richer set of data to be recorded. The `proxyTransparent` mode proxies the request but does not record any data. See below for details.
`addWaitBehavior`	`false`	boolean	If true, mountebank will add a `wait` behavior to the response with the same latency that the proxied call took. This is useful in performance testing scenarios where you want to simulate the actual latency of downstream services that you're virtualizing.
`addDecorateBehavior`	`null`	string, JavaScript	If defined, mountebank will add a `decorate` behavior to the saved response.

Parameter

Default

Type

Description

to

required

A URL without the path (e.g. http://someserver:3000 or tcp://someserver:3000)

Defines the origin server that the request should proxy to.

predicateGenerators

[]

array

An array of objects that defines how the predicates for new stubs are created. Each object in the array defines the fields to generate predicates from. See below for examples.

mode

proxyOnce

string, one of proxyOnce, proxyAlways or proxyTransparent.

Defines the replay behavior of the proxy. The default proxyOnce mode doesn't require you to explicitly do anything to replay the proxied responses. The proxyAlways mode requires you to run the mb replay command (or equivalent) to switch from record mode to replay mode, but allows a richer set of data to be recorded. The proxyTransparent mode proxies the request but does not record any data. See below for details.

addWaitBehavior

false

boolean

If true, mountebank will add a wait behavior to the response with the same latency that the proxied call took. This is useful in performance testing scenarios where you want to simulate the actual latency of downstream services that you're virtualizing.

addDecorateBehavior

null

string, JavaScript

If defined, mountebank will add a decorate behavior to the saved response.

http and https proxies add additional optional parameters:

Parameter	Default	Type	Description
`cert`	`null`	A PEM-formatted string	The SSL client certificate
`key`	`null`	A PEM-formatted string	The SSL client private key
`ciphers`	Here	A valid cipher (see this page for formats)	For older (and insecure) https servers, this field allows you to override the cipher used to communicate
`secureProtocol`	`TLS_method`	A valid OpenSSL protocol method name	The SSL method to use
`passphrase`	`null`	string	Shared passphrase used for a single private key
`injectHeaders`	`{}`	object	Key-value pairs of headers to inject into the proxied request.

Parameter

Default

Type

Description

cert

null

A PEM-formatted string

The SSL client certificate

key

null

A PEM-formatted string

The SSL client private key

ciphers

Here

A valid cipher (see this page for formats)

For older (and insecure) https servers, this field allows you to override the cipher used to communicate

secureProtocol

TLS_method

A valid OpenSSL protocol method name

The SSL method to use

passphrase

null

string

Shared passphrase used for a single private key

injectHeaders

{}

object

Key-value pairs of headers to inject into the proxied request.

tcp proxies support the following optional configuration:

Parameter	Default	Type	Description
`keepalive`	`false`	boolean	If true, mountebank will not close the connection on each proxied request

Parameter

Default

Type

Description

keepalive

false

boolean

If true, mountebank will not close the connection on each proxied request

It is occasionally useful to capture how long the original proxied request takes. mountebank stores the number of milliseconds for the request in the _proxyResponseTime field in the response. Setting the addWaitBehavior flag will add that latency to the saved response.

Note, if you use a corporate proxy, then the standard shell http_proxy or https_proxy environment variables will be honored.

Select the behavior of the proxy below for a relevant example:

Understanding predicateGenerators

<%- include('proxy/predicateGenerators') -%>

Understanding proxy modes

<%- include('proxy/proxyModes') -%>

Adding latency to the saved responses with addWaitBehavior

<%- include('proxy/addWaitBehavior') -%>

Decorating saved responses with addDecorateBehavior

<%- include('proxy/addDecorateBehavior') -%>

Changing the proxied request headers with injectHeaders

<%- include('proxy/injectHeaders') -%>