MemoryProf

MemoryProf tracks memory usage during your test suite run, and can help to detect test examples and groups that cause memory spikes. Memory profiling supports the following metrics: RSS, allocations and GC time.

Example output:

[TEST PROF INFO] MemoryProf results

Final RSS: 673KB

Top 5 groups (by RSS):

AnswersController (./spec/controllers/answers_controller_spec.rb:3) – +80KB (13.50%)
QuestionsController (./spec/controllers/questions_controller_spec.rb:3) – +32KB  (9.08%)
CommentsController (./spec/controllers/comments_controller_spec.rb:3) – +16KB (3.27%)

Top 5 examples (by RSS):

destroys question (./spec/controllers/questions_controller_spec.rb:38) – +144KB (24.38%)
change comments count (./spec/controllers/comments_controller_spec.rb:7) – +120KB (20.00%)
change Votes count (./spec/shared_examples/controllers/voted_examples.rb:23) – +90KB (16.36%)
change Votes count (./spec/shared_examples/controllers/voted_examples.rb:23) – +64KB (12.86%)
fails (./spec/shared_examples/controllers/invalid_examples.rb:3) – +32KB (5.00%)

The output shows the amount of memory used by each example and top-level example group (typically, a test file).

Instructions

To activate MemoryProf with:

RSpec

Use TEST_MEM_PROF environment variable to set which metric to use:

TEST_MEM_PROF='rss' rspec ...
TEST_MEM_PROF='alloc' rake rspec ...
TEST_MEM_PROF='gc' rake rspec ...

Minitest

In Minitest 6+, you must first activate TestProf plugin by adding Minitest.load :test_prof in your test helper.

Use TEST_MEM_PROF environment variable to set which metric to use:

TEST_MEM_PROF='rss' rake test
TEST_MEM_PROF='alloc' rake test
TEST_MEM_PROF='gc' rake test

or use CLI options as well:

# Run a specific file using CLI option
ruby test/my_super_test.rb --mem-prof=rss

# Show the list of possible options:
ruby test/my_super_test.rb --help

Configuration

By default, MemoryProf tracks the top 5 examples and groups that use the largest amount of memory. You can set how many examples/groups to display with the option:

TEST_MEM_PROF='rss' TEST_MEM_PROF_COUNT=10 rspec ...

or with CLI options for Minitest:

# Run a specific file using CLI option
ruby test/my_super_test.rb --mem-prof=rs --mem-prof-top-count=10

Supported Ruby Engines & OS

Currently the allocation mode is not supported for JRuby.

Since RSS depends on the OS, MemoryProf uses different tools to retrieve it:

• Linux – /proc/$pid/statm file,
• macOS, Solaris, BSD – ps,
• Windows – Get-Process, requires PowerShell to be installed.