# Common Test Hooks

# ct_hooks

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Module

ct_hooks

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Module Summary

A callback interface on top of Common Test.

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Since

Module ct_hooks was introduced in OTP R14B02.

###
Description

The Common Test Hook (CTH) framework allows extensions of the default behavior of Common Test by callbacks before and after all test suite calls. It is intended for advanced users of Common Test who want to abstract out behavior that is common to multiple test suites.

In brief, CTH allows you to:

- Manipulate the runtime configuration before each suite configuration call.

- Manipulate the return of all suite configuration calls and by extension the result of the test themselves.

The following sections describe the mandatory and optional CTH functions that Common Test calls during test execution. For more details, see section Common Test Hooks in the User's Guide.

For information about how to add a CTH to your suite, see section Installing a CTH in the User's Guide.

Note

For a minimal example of a CTH, see section Example CTH in the User's Guide.

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Callback Functions

The following functions define the callback interface for a CTH.

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Exports

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Module:init(Id, Opts) -> {ok, State} | {ok, State, Priority}
OTP R14B02

### Types

Id = reference() | term()
Opts = term()
State = term()
Priority = integer()

MANDATORY

This function is always called before any other callback function. Use it to initiate any common state. It is to return a state for this CTH.

Id is either the return value of ct_hooks:id/1, or a reference (created using erlang:make_ref/0 in ERTS) if ct_hooks:id/1 is not implemented.

Priority is the relative priority of this hook. Hooks with a lower priority are executed first. If no priority is specified, it is set to 0.

For details about hook execution order, see section CTH Execution Order in the User's Guide.

For details about when init is called, see section CTH Scope in the User's Guide.

####
Module:post_groups(SuiteName, GroupDefs) -> NewGroupDefs
OTP 21.3.8

### Types

SuiteName = atom()
GroupDefs = NewGroupDefs = [Group]
Group = {GroupName,Properties,GroupsAndTestCases}
GroupName = atom()
Properties = [parallel | sequence | Shuffle | {GroupRepeatType,N}]
GroupsAndTestCases = [Group | {group,GroupName} | TestCase | {testcase,TestCase,TCRepeatProps}]
TestCase = atom()
TCRepeatProps = [{repeat,N} | {repeat_until_ok,N} | {repeat_until_fail,N}]
Shuffle = shuffle | {shuffle,Seed}
Seed = {integer(),integer(),integer()}
GroupRepeatType = repeat | repeat_until_all_ok | repeat_until_all_fail | repeat_until_any_ok | repeat_until_any_fail
N = integer() | forever

OPTIONAL

This function is called after groups/0. It is used to modify the test group definitions, for instance to add or remove groups or change group properties.

GroupDefs is what groups/0 returned, that is, a list of group definitions.

NewGroupDefs is the possibly modified version of this list.

This function is called only if the CTH is added before init_per_suite is run. For details, see section CTH Scope in the User's Guide.

Notice that for CTHs that are installed by means of the suite/0 function, post_groups/2 is called before the init/2 hook function. However, for CTHs that are installed by means of the CT start flag, the init/2 function is called first.

Note

Prior to each test execution, Common Test does a simulated test run in order to count test suites, groups and cases for logging purposes. This causes the post_groups/2 hook function to always be called twice. For this reason, side effects are best avoided in this callback.

####
Module:post_all(SuiteName, Return, GroupDefs) -> NewReturn
OTP 21.3.8

### Types

SuiteName = atom()
Return = NewReturn = Tests | {skip,Reason}
Tests = [TestCase | {testcase,TestCase,TCRepeatProps} | {group,GroupName} | {group,GroupName,Properties} | {group,GroupName,Properties,SubGroups}]
TestCase = atom()
TCRepeatProps = [{repeat,N} | {repeat_until_ok,N} | {repeat_until_fail,N}]
GroupName = atom()
Properties = GroupProperties | default
SubGroups = [{GroupName,Properties} | {GroupName,Properties,SubGroups}]
Shuffle = shuffle | {shuffle,Seed}
Seed = {integer(),integer(),integer()}
GroupRepeatType = repeat | repeat_until_all_ok | repeat_until_all_fail | repeat_until_any_ok | repeat_until_any_fail
N = integer() | forever
GroupDefs = NewGroupDefs = [Group]
Group = {GroupName,GroupProperties,GroupsAndTestCases}
GroupProperties = [parallel | sequence | Shuffle | {GroupRepeatType,N}]
GroupsAndTestCases = [Group | {group,GroupName} | TestCase]
Reason = term()

OPTIONAL

This function is called after all/0. It is used to modify the set of test cases and test group to be executed, for instance to add or remove test cases and groups, change group properties, or even skip all tests in the suite.

Return is what all/0 returned, that is, a list of test cases and groups to be executed, or a tuple {skip,Reason}.

GroupDefs is what groups/0 or the post_groups/2 hook returned, that is, a list of group definitions.

NewReturn is the possibly modified version of Return.

This function is called only if the CTH is added before init_per_suite is run. For details, see section CTH Scope in the User's Guide.

Notice that for CTHs that are installed by means of the suite/0 function, post_all/2 is called before the init/2 hook function. However, for CTHs that are installed by means of the CT start flag, the init/2 function is called first.

Note

Prior to each test execution, Common Test does a simulated test run in order to count test suites, groups and cases for logging purposes. This causes the post_all/3 hook function to always be called twice. For this reason, side effects are best avoided in this callback.

####
Module:pre_init_per_suite(SuiteName, InitData, CTHState) -> Result
OTP R14B02

### Types

SuiteName = atom()
InitData = Config | SkipOrFail
Config = NewConfig = [{Key,Value}]
CTHState = NewCTHState = term()
Result = {Return, NewCTHState}
Return = NewConfig | SkipOrFail
SkipOrFail = {fail, Reason} | {skip, Reason}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called before init_per_suite if it exists. It typically contains initialization/logging that must be done before init_per_suite is called. If {skip,Reason} or {fail,Reason} is returned, init_per_suite and all test cases of the suite are skipped and Reason printed in the overview log of the suite.

SuiteName is the name of the suite to be run.

InitData is the original configuration list of the test suite, or a SkipOrFail tuple if a previous CTH has returned this.

CTHState is the current internal state of the CTH.

Return is the result of the init_per_suite function. If it is {skip,Reason} or {fail,Reason}, init_per_suite is never called, instead the initiation is considered to be skipped or failed, respectively. If a NewConfig list is returned, init_per_suite is called with that NewConfig list. For more details, see section Pre Hooks in the User's Guide.

This function is called only if the CTH is added before init_per_suite is run. For details, see section CTH Scope in the User's Guide.

####
Module:post_init_per_suite(SuiteName, Config, Return, CTHState) -> Result
OTP R14B02

### Types

SuiteName = atom()
Config = [{Key,Value}]
Return = NewReturn = Config | SkipOrFail | term()
SkipOrFail = {fail, Reason} | {skip, Reason} | term()
CTHState = NewCTHState = term()
Result = {NewReturn, NewCTHState}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called after init_per_suite if it exists. It typically contains extra checks to ensure that all the correct dependencies are started correctly.

Return is what init_per_suite returned, that is, {fail,Reason}, {skip,Reason}, a Config list, or a term describing how init_per_suite failed.

NewReturn is the possibly modified return value of init_per_suite. To recover from a failure in init_per_suite, return ConfigList with the tc_status element removed. For more details, see Post Hooks in section "Manipulating Tests" in the User's Guide.

CTHState is the current internal state of the CTH.

This function is called only if the CTH is added before or in init_per_suite. For details, see section CTH Scope in the User's Guide.

####
Module:pre_init_per_group(SuiteName, GroupName, InitData, CTHState) -> Result
OTP 19.3

### Types

SuiteName = atom()
GroupName = atom()
InitData = Config | SkipOrFail
Config = NewConfig = [{Key,Value}]
CTHState = NewCTHState = term()
Result = {NewConfig | SkipOrFail, NewCTHState}
SkipOrFail = {fail,Reason} | {skip, Reason}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called before init_per_group if it exists. It behaves the same way as pre_init_per_suite, but for function init_per_group instead.

If Module:pre_init_per_group/4 is not exported, common_test will attempt to call Module:pre_init_per_group(GroupName, InitData, CTHState) instead. This is for backwards compatibility.

####
Module:post_init_per_group(SuiteName, GroupName, Config, Return, CTHState) -> Result
OTP 19.3

### Types

SuiteName = atom()
GroupName = atom()
Config = [{Key,Value}]
Return = NewReturn = Config | SkipOrFail | term()
SkipOrFail = {fail,Reason} | {skip, Reason}
CTHState = NewCTHState = term()
Result = {NewReturn, NewCTHState}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called after init_per_group if it exists. It behaves the same way as post_init_per_suite, but for function init_per_group instead.

If Module:post_init_per_group/5 is not exported, common_test will attempt to call Module:post_init_per_group(GroupName, Config, Return, CTHState) instead. This is for backwards compatibility.

####
Module:pre_init_per_testcase(SuiteName, TestcaseName, InitData, CTHState) -> Result
OTP 19.3

### Types

SuiteName = atom()
TestcaseName = atom()
InitData = Config | SkipOrFail
Config = NewConfig = [{Key,Value}]
CTHState = NewCTHState = term()
Result = {NewConfig | SkipOrFail, NewCTHState}
SkipOrFail = {fail,Reason} | {skip, Reason}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called before init_per_testcase if it exists. It behaves the same way as pre_init_per_suite, but for function init_per_testcase instead.

If Module:pre_init_per_testcase/4 is not exported, common_test will attempt to call Module:pre_init_per_testcase(TestcaseName, InitData, CTHState) instead. This is for backwards compatibility.

CTHs cannot be added here right now. That feature may be added in a later release, but it would right now break backwards compatibility.

####
Module:post_init_per_testcase(SuiteName, TestcaseName, Config, Return, CTHState) -> Result
OTP 19.3

### Types

SuiteName = atom()
TestcaseName = atom()
Config = [{Key,Value}]
Return = NewReturn = Config | SkipOrFail | term()
SkipOrFail = {fail,Reason} | {skip, Reason}
CTHState = NewCTHState = term()
Result = {NewReturn, NewCTHState}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called after init_per_testcase if it exists. It behaves the same way as post_init_per_suite, but for function init_per_testcase instead.

If Module:post_init_per_testcase/5 is not exported, common_test will attempt to call Module:post_init_per_testcase(TestcaseName, Config, Return, CTHState) instead. This is for backwards compatibility.

####
Module:pre_end_per_testcase(SuiteName, TestcaseName, EndData, CTHState) -> Result
OTP 19.3

### Types

SuiteName = atom()
TestcaseName = atom()
EndData = Config
Config = NewConfig = [{Key,Value}]
CTHState = NewCTHState = term()
Result = {NewConfig, NewCTHState}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called before end_per_testcase if it exists. It behaves the same way as pre_end_per_suite, but for function end_per_testcase instead.

This function cannot change the result of the test case by returning skip or fail tuples, but it may insert items in Config that can be read in end_per_testcase/2 or in post_end_per_testcase/5.

If Module:pre_end_per_testcase/4 is not exported, common_test will attempt to call Module:pre_end_per_testcase(TestcaseName, EndData, CTHState) instead. This is for backwards compatibility.

####
Module:post_end_per_testcase(SuiteName, TestcaseName, Config, Return, CTHState) -> Result
OTP 19.3

### Types

SuiteName = atom()
TestcaseName = atom()
Config = [{Key,Value}]
Return = NewReturn = Config | SkipOrFail | term()
SkipOrFail = {fail,Reason} | {skip, Reason}
CTHState = NewCTHState = term()
Result = {NewReturn, NewCTHState}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called after end_per_testcase if it exists. It behaves the same way as post_end_per_suite, but for function end_per_testcase instead.

If Module:post_end_per_testcase/5 is not exported, common_test will attempt to call Module:post_end_per_testcase(TestcaseName, Config, Return, CTHState) instead. This is for backwards compatibility.

####
Module:pre_end_per_group(SuiteName, GroupName, EndData, CTHState) -> Result
OTP 19.3

### Types

SuiteName = atom()
GroupName = atom()
EndData = Config | SkipOrFail
Config = NewConfig = [{Key,Value}]
CTHState = NewCTHState = term()
Result = {NewConfig | SkipOrFail, NewCTHState}
SkipOrFail = {fail,Reason} | {skip, Reason}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called before end_per_group if it exists. It behaves the same way as pre_init_per_suite, but for function end_per_group instead.

If Module:pre_end_per_group/4 is not exported, common_test will attempt to call Module:pre_end_per_group(GroupName, EndData, CTHState) instead. This is for backwards compatibility.

####
Module:post_end_per_group(SuiteName, GroupName, Config, Return, CTHState) -> Result
OTP 19.3

### Types

SuiteName = atom()
GroupName = atom()
Config = [{Key,Value}]
Return = NewReturn = Config | SkipOrFail | term()
SkipOrFail = {fail,Reason} | {skip, Reason}
CTHState = NewCTHState = term()
Result = {NewReturn, NewCTHState}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called after end_per_group if it exists. It behaves the same way as post_init_per_suite, but for function end_per_group instead.

If Module:post_end_per_group/5 is not exported, common_test will attempt to call Module:post_end_per_group(GroupName, Config, Return, CTHState) instead. This is for backwards compatibility.

####
Module:pre_end_per_suite(SuiteName, EndData, CTHState) -> Result
OTP R14B02

### Types

SuiteName = atom()
EndData = Config | SkipOrFail
Config = NewConfig = [{Key,Value}]
CTHState = NewCTHState = term()
Result = {NewConfig | SkipOrFail, NewCTHState}
SkipOrFail = {fail,Reason} | {skip, Reason}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called before end_per_suite if it exists. It behaves the same way as pre_init_per_suite, but for function end_per_suite instead.

####
Module:post_end_per_suite(SuiteName, Config, Return, CTHState) -> Result
OTP R14B02

### Types

SuiteName = atom()
Config = [{Key,Value}]
Return = NewReturn = Config | SkipOrFail | term()
SkipOrFail = {fail,Reason} | {skip, Reason}
CTHState = NewCTHState = term()
Result = {NewReturn, NewCTHState}
Key = atom()
Value = term()
Reason = term()

OPTIONAL

This function is called after end_per_suite if it exists. It behaves the same way as post_init_per_suite, but for function end_per_suite instead.

####
Module:on_tc_fail(SuiteName, TestName, Reason, CTHState) -> NewCTHState
OTP 19.3

### Types

SuiteName = atom()
TestName = init_per_suite | end_per_suite | {init_per_group,GroupName} | {end_per_group,GroupName} | {FuncName,GroupName} | FuncName
FuncName = atom()
GroupName = atom()
Reason = term()
CTHState = NewCTHState = term()

OPTIONAL

This function is called whenever a test case (or configuration function) fails. It is called after the post function is called for the failed test case, that is:

- If init_per_suite fails, this function is called after post_init_per_suite.

- If a test case fails, this function is called after post_end_per_testcase.

If the failed test case belongs to a test case group, the first argument is a tuple {FuncName,GroupName}, otherwise only the function name.

The data that comes with Reason follows the same format as FailReason in event tc_done. For details, see section Event Handling in the User's Guide.

If Module:on_tc_fail/4 is not exported, common_test will attempt to call Module:on_tc_fail(TestName, Reason, CTHState) instead. This is for backwards compatibility.

####
Module:on_tc_skip(SuiteName, TestName, Reason, CTHState) -> NewCTHState
OTP 19.3

### Types

SuiteName = atom()
TestName = init_per_suite | end_per_suite | {init_per_group,GroupName} | {end_per_group,GroupName} | {FuncName,GroupName} | FuncName
FuncName = atom()
GroupName = atom()
Reason = {tc_auto_skip | tc_user_skip, term()}
CTHState = NewCTHState = term()

OPTIONAL

This function is called whenever a test case (or configuration function) is skipped. It is called after the post function is called for the skipped test case, that is:

- If init_per_group is skipped, this function is called after post_init_per_group.

- If a test case is skipped, this function is called after post_end_per_testcase.

If the skipped test case belongs to a test case group, the first argument is a tuple {FuncName,GroupName}, otherwise only the function name.

The data that comes with Reason follows the same format as events tc_auto_skip and tc_user_skip For details, see section Event Handling in the User's Guide.

If Module:on_tc_skip/4 is not exported, common_test will attempt to call Module:on_tc_skip(TestName, Reason, CTHState) instead. This is for backwards compatibility.

####
Module:terminate(CTHState)
OTP R14B02

### Types

CTHState = term()

OPTIONAL

This function is called at the end of a CTH scope.

####
Module:id(Opts) -> Id
OTP R14B02

### Types

Opts = term()
Id = term()

OPTIONAL

The Id identifies a CTH instance uniquely. If two CTHs return the same Id, the second CTH is ignored and subsequent calls to the CTH are only made to the first instance. For details, see section Installing a CTH in the User's Guide.

This function is not to have any side effects, as it can be called multiple times by Common Test.

If not implemented, the CTH acts as if this function returned a call to make_ref/0.