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NAME
cover - 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}, where Module is the module name.
* Level = function
Answer = [{Function,Value}], one tuple for each function in the module. A function is
specified by its module name M, function name F and arity A 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 name M, function name F, arity A and position in the function
definition C 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 name M and line number in the source file N as a tuple {M,N}.
* Analysis = coverage
Value = {Cov,NotCov} where Cov is the number of executable lines in the module,
function, clause or line that have been executed at least once and NotCov 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:
Pid = pid()
Reason = {already_started,Pid}
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:
Nodes = StartedNodes = [atom()]
Starts a Cover server on the each of given nodes, and loads all cover compiled
modules.
compile(ModFile) -> Result
compile(ModFile, Options) -> Result
compile_module(ModFile) -> Result
compile_module(ModFile, Options) -> Result
Types:
ModFile = Module | File
Module = atom()
File = string()
Options = [Option]
Option = {i,Dir} | {d,Macro} | {d,Macro,Value}
See compile:file/2.
Result = {ok,Module} | {error,File} | {error,not_main_node}
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.
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:
Dir = string()
Options = [Option]
See compile_module/1,2
Result = {ok,Module} | {error,File} | {error,not_main_node}
See compile_module/1,2
Reason = eacces | enoent
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(ModFile) -> Result
Types:
ModFile = Module | BeamFile
Module = atom()
BeamFile = string()
Result = {ok,Module} | {error,BeamFile} | {error,Reason}
Reason = non_existing | {no_abstract_code,BeamFile} |
{encrypted_abstract_code,BeamFile} |
{already_cover_compiled,no_beam_found,Module} | not_main_node
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.
compile_beam_directory() -> [Result] | {error,Reason}
compile_beam_directory(Dir) -> [Result] | {error,Reason}
Types:
Dir = string()
Result = See compile_beam/1
Reason = eacces | enoent
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(Module) -> {ok,Answer} | {error,Error}
analyse(Module, Analysis) -> {ok,Answer} | {error,Error}
analyse(Module, Level) -> {ok,Answer} | {error,Error}
analyse(Module, Analysis, Level) -> {ok,Answer} | {error,Error}
Types:
Module = atom()
Analysis = coverage | calls
Level = line | clause | function | module
Answer = {Module,Value} | [{Item,Value}]
Item = Line | Clause | Function
Line = {M,N}
Clause = {M,F,A,C}
Function = {M,F,A}
M = F = atom()
N = A = C = integer()
Value = {Cov,NotCov} | Calls
Cov = NotCov = Calls = integer()
Error = {not_cover_compiled,Module} | not_main_node
Performs analysis of a Cover compiled module Module, 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 Module is not Cover compiled, the function returns
{error,{not_cover_compiled,Module}}.
HINT: It is possible to issue multiple analyse_to_file commands at the same time.
analyse_to_file(Module) ->
analyse_to_file(Module,Options) ->
analyse_to_file(Module, OutFile) ->
analyse_to_file(Module, OutFile, Options) -> {ok,OutFile} | {error,Error}
Types:
Module = atom()
OutFile = string()
Options = [Option]
Option = html
Error = {not_cover_compiled,Module} | {file,File,Reason} | no_source_code_found
| not_main_node
File = string()
Reason = term()
Makes a copy OutFile of the source file for a module Module, 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 Module is not Cover compiled, the function returns
{error,{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 the 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, {error,no_source_code_found} is returned.
HINT: It is possible to issue multiple analyse_to_file commands at the same time.
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:
Module = atom()
OutFile = string()
Options = [Option]
Option = html
Error = {not_cover_compiled,Module} | {file,File,Reason} | no_source_code_found
| not_main_node
File = string()
Reason = term()
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:
Module = atom()
Returns a list with all modules that are currently Cover compiled.
imported_modules() -> [Module] | {error,not_main_node}
Types:
Module = atom()
Returns a list with all modules for which there are imported data.
imported() -> [File] | {error,not_main_node}
Types:
File = string()
Returns a list with all imported files.
which_nodes() -> [Node] | {error,not_main_node}
Types:
Node = atom()
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:
Module = atom()
Beam = string()
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:
Module = atom()
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:
ExportFile = string()
Module = atom()
Reason = {not_cover_compiled,Module} | {cant_open_file,ExportFile,Reason} |
not_main_node
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:
ExportFile = string()
Reason = {cant_open_file,ExportFile,Reason} | not_main_node
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:
Nodes = [atom()]
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:
Nodes = [atom()]
Fetch data from the Cover database on the remote nodes and stored on the main node.
SEE ALSO
code(3erl), compile(3erl)