CheatRSpec Ruby testing
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Start here
rspecRun the whole suite
rspec <file>
Run one spec file
rspec <file>:<line>
Run the example at a line
rspec -e "<text>"
Run by name
rspec --only-failures
Rerun what failed
rspec --fail-fast
Stop at first failure
rspec --format doc
Readable output
rspec --initCreate .rspec and spec_helper
Concepts
Example group
describe / context
Nested group
context, before, let
Example it { expect ... }
Run
rspecRun all specs
rspec <file> <dir>
Run files or directories
rspec <file>:<line>
Run example or group at that line
Line inside a group runs the whole group.
rspec <file>[1:2]
Run by id (nested index)
Ids like ./a_spec.rb[1:2] are what --bisect prints.
rspec --dry-runList examples without running them
rspec --versionShow the RSpec version
Filter
rspec -e "<text>"
Run examples whose name contains text
Matches the full nested description; repeat -e for more.
rspec -E "<regex>"
Run examples matching a regex
rspec --tag <tag>
Run examples with a tag
rspec --tag ~<tag>
Skip examples with a tag
Quote the tilde in some shells.
rspec --tag <key>:<value>
Match tag with a value
rspec --only-failures
Run last run's failures
Set config.example_status_persistence_file_path (e.g. to a
spec/ file).
rspec --next-failure
Fix failures one at a time
Same as --only-failures --fail-fast --order defined.
Output
rspec --format doc
Nested, readable output
rspec -f pDots, the default progress
rspec -f failures
Only failures, one line each
rspec -f json -o <file>
Write JSON results to a file
-o applies to the preceding -f; repeat both for several
outputs.
rspec --profileShow the 10 slowest examples
rspec --profile <n>
Show the n slowest examples
rspec -bFull backtraces
Failures and order
rspec --fail-fast
Stop after the first failure
rspec --fail-fast=<n>
Stop after n failures
rspec --seed <n>
Rerun with a random order seed
The seed is printed at the end of a randomised run.
rspec --order random
Shuffle example order
rspec --order defined
Run in file order
rspec --bisectFind the minimal failing set
Needs a failing run; combine with --seed <n>.
Writing specs
RSpec.describe <Class> do
Top-level example group
describe "#<method>" do
Group for one method
context "when <state>" do
Group for one situation
it "<behaviour>" do
One example
let(:<name>) { <value> }
Lazy, per-example helper
Evaluated on first use; let! evaluates before each example.
subject { <expr> }
Object under test
before { <setup> }
Run before each example
after { <cleanup> }
Run after each example
before(:all) { <setup> }
Run once per group
State leaks between examples; prefer before(:each) or let.
around { |ex| <x>; ex.run }
Wrap each example
it "<x>", :<tag> do
Tag one example
shared_examples "<name>" do
Define reusable examples
it_behaves_like "<name>"
Include shared examples (nested)
shared_context "<name>" do
Reusable setup
skip "<reason>"
Skip an example
described_classThe class passed to describe
Expectations
expect(<x>).to eq(<y>)
Value equals
expect(<x>).not_to eq(<y>)
Value differs
expect(<x>).to be_truthy
Truthy value
expect(<x>).to be_nil
Value is nil
expect(<x>).to be_a(<Class>)
Is instance of class
expect(<x>).to include(<y>)
Collection or string contains
expect(<x>).to match(<regex>)
String matches regex
expect(<x>).to
be_within(<d>).of(<n>)
Number near another
expect(<a>).to match_array(<b>)
Same elements, any order
expect { <code> }.to raise_error(<Error>)
Block raises an error
expect { <code> }.to change { <x>
}.by(<n>)
Block changes a value
expect(<x>).to be_<predicate>
Calls <predicate>? on the object
be_empty calls empty?, be_valid calls valid?.
Mocks
double("<name>", <m>: <v>)
Stand-in object
instance_double(<Class>)
Double checked against a class
Fails if the method does not exist on the class.
allow(<obj>).to
receive(:<m>).and_return(<v>)
Stub a method
expect(<obj>).to
receive(:<m>).with(<args>)
Expect a call
expect(<obj>).to have_received(:<m>)
Assert a call after the fact
Needs allow or a spy first.
Config
.rspecDefault CLI options, one per line
Put --require spec_helper here.
RSpec.configure do |c|
Global configuration block
c.order = :random
Randomise order by default
c.default_formatter = "doc"
Doc output when run on one file
Recipes
rspec spec/models/user_spec.rb:42rspec --next-failurerspec -b -e "validates email"rspec --order random # note the printed seedrspec --seed 4711 --bisect# run the minimal command bisect prints# spec/spec_helper.rbRSpec.configure do |c| c.filter_run_when_matching :focus c.order = :randomend# then: fit "works" do ... endbundle exec rspec \ --format progress \ --format json --out tmp/rspec.json \ --fail-fast=5
