module Coverage - Documentation for Ruby 3.4
Description: module Coverage: Coverage provides coverage measurement feature for Ruby. This feature is experimental, so these APIs may be changed in future.
Keywords: ruby,module,Coverage

# module Coverage

`Coverage` provides coverage measurement feature for Ruby. This feature is experimental, so these APIs may be changed in future.

Caveat: Currently, only process-global coverage measurement is supported. You cannot measure per-thread coverage.

# Usage¶ ↑

1. require “coverage”

2. do `Coverage.start`

3. require or load Ruby source file

4. `Coverage.result` will return a hash that contains filename as key and coverage array as value. A coverage array gives, for each line, the number of line execution by the interpreter. A `nil` value means coverage is disabled for this line (lines like `else` and `end`).

# Examples¶ ↑

    [foo.rb]
    s = 0
    10.times do |x|
      s += x
    end

    if s == 45
      p :ok
    else
      p :ng
    end
    [EOF]

    require "coverage"
    Coverage.start
    require "foo.rb"
    p Coverage.result  #=> {"foo.rb"=>[1, 1, 10, nil, nil, 1, 1, nil, 0, nil]}

## Lines `Coverage`¶ ↑

If a coverage mode is not explicitly specified when starting coverage, lines coverage is what will run. It reports the number of line executions for each line.

    require "coverage"
    Coverage.start(lines: true)
    require "foo.rb"
    p Coverage.result #=> {"foo.rb"=>{:lines=>[1, 1, 10, nil, nil, 1, 1, nil, 0, nil]}}

The value of the lines coverage result is an array containing how many times each line was executed. Order in this array is important. For example, the first item in this array, at index 0, reports how many times line 1 of this file was executed while coverage was run (which, in this example, is one time).

A `nil` value means coverage is disabled for this line (lines like `else` and `end`).

## Oneshot Lines `Coverage`¶ ↑

Oneshot lines coverage tracks and reports on the executed lines while coverage is running. It will not report how many times a line was executed, only that it was executed.

    require "coverage"
    Coverage.start(oneshot_lines: true)
    require "foo.rb"
    p Coverage.result #=> {"foo.rb"=>{:oneshot_lines=>[1, 2, 3, 6, 7]}}

The value of the oneshot lines coverage result is an array containing the line numbers that were executed.

## Branches `Coverage`¶ ↑

Branches coverage reports how many times each branch within each conditional was executed.

    require "coverage"
    Coverage.start(branches: true)
    require "foo.rb"
    p Coverage.result #=> {"foo.rb"=>{:branches=>{[:if, 0, 6, 0, 10, 3]=>{[:then, 1, 7, 2, 7, 7]=>1, [:else, 2, 9, 2, 9, 7]=>0}}}}

Each entry within the branches hash is a conditional, the value of which is another hash where each entry is a branch in that conditional. The values are the number of times the method was executed, and the keys are identifying information about the branch.

The information that makes up each key identifying branches or conditionals is the following, from left to right:

1. A label for the type of branch or conditional.

2. A unique identifier.

3. The starting line number it appears on in the file.

4. The starting column number it appears on in the file.

5. The ending line number it appears on in the file.

6. The ending column number it appears on in the file.

## Methods `Coverage`¶ ↑

Methods coverage reports how many times each method was executed.

    [foo_method.rb]
    class Greeter
      def greet
        "welcome!"
      end
    end

    def hello
      "Hi"
    end

    hello()
    Greeter.new.greet()
    [EOF]

    require "coverage"
    Coverage.start(methods: true)
    require "foo_method.rb"
    p Coverage.result #=> {"foo_method.rb"=>{:methods=>{[Object, :hello, 7, 0, 9, 3]=>1, [Greeter, :greet, 2, 2, 4, 5]=>1}}}

Each entry within the methods hash represents a method. The values in this hash are the number of times the method was executed, and the keys are identifying information about the method.

The information that makes up each key identifying a method is the following, from left to right:

1. The class.

2. The method name.

3. The starting line number the method appears on in the file.

4. The starting column number the method appears on in the file.

5. The ending line number the method appears on in the file.

6. The ending column number the method appears on in the file.

## All `Coverage` Modes¶ ↑

You can also run all modes of coverage simultaneously with this shortcut. Note that running all coverage modes does not run both lines and oneshot lines. Those modes cannot be run simultaneously. Lines coverage is run in this case, because you can still use it to determine whether or not a line was executed.

    require "coverage"
    Coverage.start(:all)
    require "foo.rb"
    p Coverage.result #=> {"foo.rb"=>{:lines=>[1, 1, 10, nil, nil, 1, 1, nil, 0, nil], :branches=>{[:if, 0, 6, 0, 10, 3]=>{[:then, 1, 7, 2, 7, 7]=>1, [:else, 2, 9, 2, 9, 7]=>0}}, :methods=>{}}}

### Public Class Methods

line_stub (file)
Source

    # File ext/coverage/lib/coverage.rb, line 4
    def self.line_stub(file)
      lines = File.foreach(file).map { nil }
      iseqs = [RubyVM::InstructionSequence.compile_file(file)]
      until iseqs.empty?
        iseq = iseqs.pop
        iseq.trace_points.each {|n, type| lines[n - 1] = 0 if type == :line }
        iseq.each_child {|child| iseqs << child }
      end
      lines
    end

peek_result → hash
Source

    static VALUE
    rb_coverage_peek_result(VALUE klass)
    {
        VALUE coverages = rb_get_coverages();
        VALUE ncoverages = rb_hash_new();
        if (!RTEST(coverages)) {
            rb_raise(rb_eRuntimeError, "coverage measurement is not enabled");
        }
        OBJ_WB_UNPROTECT(coverages);

        rb_hash_foreach(coverages, coverage_peek_result_i, ncoverages);

        if (current_mode & COVERAGE_TARGET_METHODS) {
            rb_objspace_each_objects(method_coverage_i, &ncoverages);
        }

        rb_hash_freeze(ncoverages);
        return ncoverages;
    }

Returns a hash that contains filename as key and coverage array as value. This is the same as ‘Coverage.result(stop: false, clear: false)`.

    {
      "file.rb" => [1, 2, nil],
      ...
    }

result(stop: true, clear: true) → hash
Source

    static VALUE
    rb_coverage_result(int argc, VALUE *argv, VALUE klass)
    {
        VALUE ncoverages;
        VALUE opt;
        int stop = 1, clear = 1;

        if (current_state == IDLE) {
            rb_raise(rb_eRuntimeError, "coverage measurement is not enabled");
        }

        rb_scan_args(argc, argv, "01", &opt);

        if (argc == 1) {
            opt = rb_convert_type(opt, T_HASH, "Hash", "to_hash");
            stop = RTEST(rb_hash_lookup(opt, ID2SYM(rb_intern("stop"))));
            clear = RTEST(rb_hash_lookup(opt, ID2SYM(rb_intern("clear"))));
        }

        ncoverages = rb_coverage_peek_result(klass);
        if (stop && !clear) {
            rb_warn("stop implies clear");
            clear = 1;
        }
        if (clear) {
            rb_clear_coverages();
            if (!NIL_P(me2counter)) rb_hash_foreach(me2counter, clear_me2counter_i, Qnil);
        }
        if (stop) {
            if (current_state == RUNNING) {
                rb_coverage_suspend(klass);
            }
            rb_reset_coverages();
            me2counter = Qnil;
            current_state = IDLE;
        }
        return ncoverages;
    }

Returns a hash that contains filename as key and coverage array as value. If `clear` is true, it clears the counters to zero. If `stop` is true, it disables coverage measurement.

resume → nil
Source

    VALUE
    rb_coverage_resume(VALUE klass)
    {
        if (current_state == IDLE) {
            rb_raise(rb_eRuntimeError, "coverage measurement is not set up yet");
        }
        if (current_state == RUNNING) {
            rb_raise(rb_eRuntimeError, "coverage measurement is already running");
        }
        rb_resume_coverages();
        current_state = RUNNING;
        return Qnil;
    }

Start/resume the coverage measurement.

Caveat: Currently, only process-global coverage measurement is supported. You cannot measure per-thread coverage. If your process has multiple thread, using `Coverage.resume`/suspend to capture code coverage executed from only a limited code block, may yield misleading results.

running? → bool
Source

    static VALUE
    rb_coverage_running(VALUE klass)
    {
        return current_state == RUNNING ? Qtrue : Qfalse;
    }

Returns true if coverage stats are currently being collected (after `Coverage.start` call, but before `Coverage.result` call)

setup → nil
setup(:all) → nil
setup(lines: bool, branches: bool, methods: bool, eval: bool) → nil
setup(oneshot_lines: true) → nil
Source

    static VALUE
    rb_coverage_setup(int argc, VALUE *argv, VALUE klass)
    {
        VALUE coverages, opt;
        int mode;

        if (current_state != IDLE) {
            rb_raise(rb_eRuntimeError, "coverage measurement is already setup");
        }

        rb_scan_args(argc, argv, "01", &opt);

        if (argc == 0) {
            mode = 0; /* compatible mode */
        }
        else if (opt == ID2SYM(rb_intern("all"))) {
            mode = COVERAGE_TARGET_LINES | COVERAGE_TARGET_BRANCHES | COVERAGE_TARGET_METHODS | COVERAGE_TARGET_EVAL;
        }
        else {
            mode = 0;
            opt = rb_convert_type(opt, T_HASH, "Hash", "to_hash");

            if (RTEST(rb_hash_lookup(opt, ID2SYM(rb_intern("lines")))))
                mode |= COVERAGE_TARGET_LINES;
            if (RTEST(rb_hash_lookup(opt, ID2SYM(rb_intern("branches")))))
                mode |= COVERAGE_TARGET_BRANCHES;
            if (RTEST(rb_hash_lookup(opt, ID2SYM(rb_intern("methods")))))
                mode |= COVERAGE_TARGET_METHODS;
            if (RTEST(rb_hash_lookup(opt, ID2SYM(rb_intern("oneshot_lines"))))) {
                if (mode & COVERAGE_TARGET_LINES)
                    rb_raise(rb_eRuntimeError, "cannot enable lines and oneshot_lines simultaneously");
                mode |= COVERAGE_TARGET_LINES;
                mode |= COVERAGE_TARGET_ONESHOT_LINES;
            }
            if (RTEST(rb_hash_lookup(opt, ID2SYM(rb_intern("eval")))))
                mode |= COVERAGE_TARGET_EVAL;
        }

        if (mode & COVERAGE_TARGET_METHODS) {
            me2counter = rb_ident_hash_new();
        }
        else {
            me2counter = Qnil;
        }

        coverages = rb_get_coverages();
        if (!RTEST(coverages)) {
            coverages = rb_hash_new();
            rb_obj_hide(coverages);
            current_mode = mode;
            if (mode == 0) mode = COVERAGE_TARGET_LINES;
            rb_set_coverages(coverages, mode, me2counter);
            current_state = SUSPENDED;
        }
        else if (current_mode != mode) {
            rb_raise(rb_eRuntimeError, "cannot change the measuring target during coverage measurement");
        }

        return Qnil;
    }

Set up the coverage measurement.

Note that this method does not start the measurement itself. Use `Coverage.resume` to start the measurement.

You may want to use `Coverage.start` to setup and then start the measurement.

start → nil
start(:all) → nil
start(lines: bool, branches: bool, methods: bool, eval: bool) → nil
start(oneshot_lines: true) → nil
Source

    static VALUE
    rb_coverage_start(int argc, VALUE *argv, VALUE klass)
    {
        rb_coverage_setup(argc, argv, klass);
        rb_coverage_resume(klass);
        return Qnil;
    }

Enables the coverage measurement. See the documentation of `Coverage` class in detail. This is equivalent to `Coverage.setup` and `Coverage.resume`.

state → :idle, :suspended, :running
Source

    static VALUE
    rb_coverage_state(VALUE klass)
    {
        switch (current_state) {
            case IDLE: return ID2SYM(rb_intern("idle"));
            case SUSPENDED: return ID2SYM(rb_intern("suspended"));
            case RUNNING: return ID2SYM(rb_intern("running"));
        }
        return Qnil;
    }

Returns the state of the coverage measurement.

supported?(mode) → true or false
Source

    static VALUE
    rb_coverage_supported(VALUE self, VALUE _mode)
    {
        ID mode = RB_SYM2ID(_mode);

        return RBOOL(
            mode == rb_intern("lines") ||
            mode == rb_intern("oneshot_lines") ||
            mode == rb_intern("branches") ||
            mode == rb_intern("methods") ||
            mode == rb_intern("eval")
        );
    }

Returns true if coverage measurement is supported for the given mode.

The mode should be one of the following symbols: `:lines`, `:oneshot_lines`, `:branches`, `:methods`, `:eval`.

Example:

    Coverage.supported?(:lines)  #=> true
    Coverage.supported?(:all)    #=> false

suspend → nil
Source

    VALUE
    rb_coverage_suspend(VALUE klass)
    {
        if (current_state != RUNNING) {
            rb_raise(rb_eRuntimeError, "coverage measurement is not running");
        }
        rb_suspend_coverages();
        current_state = SUSPENDED;
        return Qnil;
    }

Suspend the coverage measurement. You can use `Coverage.resume` to restart the measurement.