cover
Module
cover
Module Summary
A Coverage Analysis Tool for Erlang
Description
The module cover
provides a set of functions for coverage analysis of Erlang programs, counting how many times each executable line of code is executed when a program is run.
An executable line contains an Erlang expression such as a matching or a function call. A blank line or a line containing a comment, function head or pattern in a case
- or receive
statement is not executable.
Coverage analysis can be used to verify test cases, making sure all relevant code is covered, and may also be helpful when looking for bottlenecks in the code.
Before any analysis can take place, the involved modules must be Cover compiled. This means that some extra information is added to the module before it is compiled into a binary which then is loaded. The source file of the module is not affected and no .beam
file is created.
Each time a function in a Cover compiled module is called, information about the call is added to an internal database of Cover. The coverage analysis is performed by examining the contents of the Cover database. The output Answer
is determined by two parameters, Level
and Analysis
.
-
Level = module
Answer = {Module,Value}
, whereModule
is the module name. -
Level = function
Answer = [{Function,Value}]
, one tuple for each function in the module. A function is specified by its module nameM
, function nameF
and arityA
as a tuple{M,F,A}
. -
Level = clause
Answer = [{Clause,Value}]
, one tuple for each clause in the module. A clause is specified by its module nameM
, function nameF
, arityA
and position in the function definitionC
as a tuple{M,F,A,C}
. -
Level = line
Answer = [{Line,Value}]
, one tuple for each executable line in the module. A line is specified by its module nameM
and line number in the source fileN
as a tuple{M,N}
. -
Analysis = coverage
Value = {Cov,NotCov}
whereCov
is the number of executable lines in the module, function, clause or line that have been executed at least once andNotCov
is the number of executable lines that have not been executed. -
Analysis = calls
Value = Calls
which is the number of times the module, function, or clause has been called. In the case of line level analysis,Calls
is the number of times the line has been executed.
Distribution
Cover can be used in a distributed Erlang system. One of the nodes in the system must then be selected as the main node, and all Cover commands must be executed from this node. The error reason not_main_node
is returned if an interface function is called on one of the remote nodes.
Use cover:start/1
and cover:stop/1
to add or remove nodes. The same Cover compiled code will be loaded on each node, and analysis will collect and sum up coverage data results from all nodes.
To only collect data from remote nodes without stopping cover
on those nodes, use cover:flush/1
If the connection to a remote node goes down, the main node will mark it as lost. If the node comes back it will be added again. If the remote node was alive during the disconnected periode, cover data from before and during this periode will be included in the analysis.
Exports
start() -> {ok,Pid} | {error,Reason}
Types
Starts the Cover server which owns the Cover internal database. This function is called automatically by the other functions in the module.
start(Nodes) -> {ok,StartedNodes} | {error,not_main_node}
Types
Starts a Cover server on the each of given nodes, and loads all cover compiled modules.
compile(ModFiles) -> Result | [Result]
compile(ModFiles, Options) -> Result | [Result]
compile_module(ModFiles) -> Result | [Result]
compile_module(ModFiles, Options) -> Result | [Result]
Types
Seecompile:file/2.
Compiles a module for Cover analysis. The module is given by its module name Module
or by its file name File
. The .erl
extension may be omitted. If the module is located in another directory, the path has to be specified.
Options
is a list of compiler options which defaults to []
. Only options defining include file directories and macros are passed to compile:file/2
, everything else is ignored.
If the module is successfully Cover compiled, the function returns {ok,Module}
. Otherwise the function returns {error,File}
. Errors and warnings are printed as they occur.
If a list of ModFiles
is given as input, a list of Result
will be returned. The order of the returned list is undefined.
Note that the internal database is (re-)initiated during the compilation, meaning any previously collected coverage data for the module will be lost.
compile_directory() -> [Result] | {error,Reason}
compile_directory(Dir) -> [Result] | {error,Reason}
compile_directory(Dir, Options) -> [Result] | {error,Reason}
Types
Seecompile_module/1,2
See compile_module/1,2
Compiles all modules (.erl
files) in a directory Dir
for Cover analysis the same way as compile_module/1,2
and returns a list with the return values.
Dir
defaults to the current working directory.
The function returns {error,eacces}
if the directory is not readable or {error,enoent}
if the directory does not exist.
compile_beam(ModFiles) -> Result | [Result]
Types
Does the same as compile/1,2
, but uses an existing .beam
file as base, i.e. the module is not compiled from source. Thus compile_beam/1
is faster than compile/1,2
.
Note that the existing .beam
file must contain abstract code, i.e. it must have been compiled with the debug_info
option. If not, the error reason {no_abstract_code,BeamFile}
is returned. If the abstract code is encrypted, and no key is available for decrypting it, the error reason {encrypted_abstract_code,BeamFile}
is returned.
If only the module name (i.e. not the full name of the .beam
file) is given to this function, the .beam
file is found by calling code:which(Module)
. If no .beam
file is found, the error reason non_existing
is returned. If the module is already cover compiled with compile_beam/1
, the .beam
file will be picked from the same location as the first time it was compiled. If the module is already cover compiled with compile/1,2
, there is no way to find the correct .beam
file, so the error reason {already_cover_compiled,no_beam_found,Module}
is returned.
{error,BeamFile}
is returned if the compiled code can not be loaded on the node.
If a list of ModFiles
is given as input, a list of Result
will be returned. The order of the returned list is undefined.
compile_beam_directory() -> [Result] | {error,Reason}
compile_beam_directory(Dir) -> [Result] | {error,Reason}
Types
Compiles all modules (.beam
files) in a directory Dir
for Cover analysis the same way as compile_beam/1
and returns a list with the return values.
Dir
defaults to the current working directory.
The function returns {error,eacces}
if the directory is not readable or {error,enoent}
if the directory does not exist.
analyse() -> {result,Ok,Fail} | {error,not_main_node}
analyse(Modules) -> OneResult | {result,Ok,Fail} | {error,not_main_node}
analyse(Analysis) -> {result,Ok,Fail} | {error,not_main_node}
analyse(Level) -> {result,Ok,Fail} | {error,not_main_node}
analyse(Modules, Analysis) -> OneResult | {result,Ok,Fail} | {error,not_main_node}
analyse(Modules, Level) -> OneResult | {result,Ok,Fail} | {error,not_main_node}
analyse(Analysis, Level) -> {result,Ok,Fail} | {error,not_main_node}
analyse(Modules, Analysis, Level) -> OneResult | {result,Ok,Fail} | {error,not_main_node}
Types
Performs analysis of one or more Cover compiled modules, as specified by Analysis
and Level
(see above), by examining the contents of the internal database.
Analysis
defaults to coverage
and Level
defaults to function
.
If Modules
is an atom (one module), the return will be OneResult
, else the return will be {result,Ok,Fail}
.
If Modules
is not given, all modules that have data in the cover data table, are analysed. Note that this includes both cover compiled modules and imported modules.
If a given module is not Cover compiled, this is indicated by the error reason {not_cover_compiled,Module}
.
analyse_to_file() -> {result,Ok,Fail} | {error,not_main_node}
analyse_to_file(Modules) -> Answer | {result,Ok,Fail} | {error,not_main_node}
analyse_to_file(Options) -> {result,Ok,Fail} | {error,not_main_node}
analyse_to_file(Modules,Options) -> Answer | {result,Ok,Fail} | {error,not_main_node}
Types
Makes copies of the source file for the given modules, where it for each executable line is specified how many times it has been executed.
The output file OutFile
defaults to Module.COVER.out
, or Module.COVER.html
if the option html
was used.
If Modules
is an atom (one module), the return will be Answer
, else the return will be a list, {result,Ok,Fail}
.
If Modules
is not given, all modules that have data in the cover data table, are analysed. Note that this includes both cover compiled modules and imported modules.
If a module is not Cover compiled, this is indicated by the error reason {not_cover_compiled,Module}
.
If the source file and/or the output file cannot be opened using file:open/2
, the function returns {error,{file,File,Reason}}
where File
is the file name and Reason
is the error reason.
If a module was cover compiled from the .beam
file, i.e. using compile_beam/1
or compile_beam_directory/0,1
, it is assumed that the source code can be found in the same directory as the .beam
file, in ../src
relative to that directory, or using the source path in Module:module_info(compile)
. When using the latter, two paths are examined: first the one constructed by joining ../src
and the tail of the compiled path below a trailing src
component, then the compiled path itself. If no source code is found, this is indicated by the error reason {no_source_code_found,Module}
.
async_analyse_to_file(Module) ->
async_analyse_to_file(Module,Options) ->
async_analyse_to_file(Module, OutFile) ->
async_analyse_to_file(Module, OutFile, Options) -> pid()
Types
This function works exactly the same way as analyse_to_file
except that it is asynchronous instead of synchronous. The spawned process will link with the caller when created. If an Error
occurs while doing the cover analysis the process will crash with the same error reason as analyse_to_file
would return.
modules() -> [Module] | {error,not_main_node}
Types
Returns a list with all modules that are currently Cover compiled.
imported_modules() -> [Module] | {error,not_main_node}
Types
Returns a list with all modules for which there are imported data.
imported() -> [File] | {error,not_main_node}
Types
Returns a list with all imported files.
which_nodes() -> [Node] | {error,not_main_node}
Types
Returns a list with all nodes that are part of the coverage analysis. Note that the current node is not returned. This node is always part of the analysis.
is_compiled(Module) -> {file,File} | false | {error,not_main_node}
Types
Returns {file,File}
if the module Module
is Cover compiled, or false
otherwise. File
is the .erl
file used by cover:compile_module/1,2
or the .beam
file used by compile_beam/1
.
reset(Module) ->
reset() -> ok | {error,not_main_node}
Types
Resets all coverage data for a Cover compiled module Module
in the Cover database on all nodes. If the argument is omitted, the coverage data will be reset for all modules known by Cover.
If Module
is not Cover compiled, the function returns {error,{not_cover_compiled,Module}}
.
export(ExportFile)
export(ExportFile,Module) -> ok | {error,Reason}
Types
Exports the current coverage data for Module
to the file ExportFile
. It is recommended to name the ExportFile
with the extension .coverdata
, since other filenames can not be read by the web based interface to cover.
If Module
is not given, data for all Cover compiled or earlier imported modules is exported.
This function is useful if coverage data from different systems is to be merged.
See also cover:import/1
import(ExportFile) -> ok | {error,Reason}
Types
Imports coverage data from the file ExportFile
created with cover:export/1,2
. Any analysis performed after this will include the imported data.
Note that when compiling a module all existing coverage data is removed, including imported data. If a module is already compiled when data is imported, the imported data is added to the existing coverage data.
Coverage data from several export files can be imported into one system. The coverage data is then added up when analysing.
Coverage data for a module can not be imported from the same file twice unless the module is first reset or compiled. The check is based on the filename, so you can easily fool the system by renaming your export file.
See also cover:export/1,2
stop() -> ok | {error,not_main_node}
Stops the Cover server and unloads all Cover compiled code.
stop(Nodes) -> ok | {error,not_main_node}
Types
Stops the Cover server and unloads all Cover compiled code on the given nodes. Data stored in the Cover database on the remote nodes is fetched and stored on the main node.
flush(Nodes) -> ok | {error,not_main_node}
Types
Fetch data from the Cover database on the remote nodes and stored on the main node.
See also
code(3), compile(3)
© 2010–2017 Ericsson AB
Licensed under the Apache License, Version 2.0.