Test only one it or describe with Rspec - ruby-on-rails-3

Question

On TestUnit you can launch one test in file with -n option
for example
require 'test_helper'
class UserTest < ActiveSupport::TestCase
test "the truth" do
assert true
end
test "the truth 2" do
assert true
end
end
You can execute only the test the truth
ruby -Itest test/unit/user_test.rb -n test_the_truth
The ouput
1 tests, 1 assertions, 0 failures, 0 errors, 0 skip
How can that with rspec ?
The command seem not work
rspec spec/models/user_spec.rb -e "User the truth"

Answer 1

You didn't include the source of your spec, so it's hard to say where the problem is, but in general you can use the -e option to run a single example. Given this spec:
# spec/models/user_spec.rb
require 'spec_helper'
describe User do
it "is true" do
true.should be_true
end
describe "validation" do
it "is also true" do
true.should be_true
end
end
end
This command line:
rspec spec/models/user_spec.rb -e "User is true"
Will produce this output:
Run filtered including {:full_description=>/(?-mix:User\ is\ true)/}
.
Finished in 0.2088 seconds
1 example, 0 failures
And if you wanted to invoke the other example, the one nested inside the validation group, you'd use this:
rspec spec/models/user_spec.rb -e "User validation is also true"
Or to run all the examples in the validation group:
rspec spec/models/user_spec.rb -e "User validation"

Answer 2

You can also select in which line is the test case you want to execute.
rspec spec/models/user_spec.rb:8
By passing any line inside the scope of the test case, only this test case will be executed. You can also use this to execute a whole context inside your test.

Answer 3

At least in Rspec 2.11.1 you can use all of the following options:
** Filtering/tags **
In addition to the following options for selecting specific files, groups,
or examples, you can select a single example by appending the line number to
the filename:
rspec path/to/a_spec.rb:37
-P, --pattern PATTERN Load files matching pattern (default: "spec/**/*_spec.rb").
-e, --example STRING Run examples whose full nested names include STRING (may be
used more than once)
-l, --line_number LINE Specify line number of an example or group (may be
used more than once).
-t, --tag TAG[:VALUE] Run examples with the specified tag, or exclude examples
by adding ~ before the tag.
- e.g. ~slow
- TAG is always converted to a symbol