ExUnit v1.2.6 ExUnit.Assertions
This module contains a set of assertion functions that are imported by default into your test cases.
In general, a developer will want to use the general
assert macro in tests. This macro introspects your code
and provide good reporting whenever there is a failure.
For example, assert some_fun() == 10 will fail (assuming
some_fun() returns 13):
Comparison (using ==) failed in:
code: some_fun() == 10
lhs: 13
rhs: 10This module also provides other convenience functions
like assert_in_delta and assert_raise to easily handle
other common cases such as checking a floating point number
or handling exceptions.
Summary
Functions
Asserts value is true, displaying the given message otherwise
Asserts that value1 and value2 differ by no more than delta
Asserts the exception is raised during function execution.
Returns the rescued exception, fails otherwise
Fails with a message
Asserts value is nil or false (that is, value is not truthy)
Asserts value1 and value2 are not within delta
Macros
Asserts its argument is a truthy value
Asserts a message was or is going to be received
Asserts a message was received and is in the current process’ mailbox. Timeout is set to 0, so there is no waiting time
Asserts expression will cause an error.
Returns the error or fails otherwise
Asserts expression will exit.
Returns the exit status/message or fails otherwise
Asserts expression will throw a value.
Returns the thrown value or fails otherwise
A negative assertion, expects the expression to be false or nil
Asserts message was not received (and won’t be received) within
the timeout period
Asserts a message was not received (i.e. it is not in the current process mailbox).
The not_expected argument must be a match pattern
Functions
Asserts value is true, displaying the given message otherwise.
Examples
assert false, "it will never be true"Asserts that value1 and value2 differ by no more than delta.
Examples
assert_in_delta 1.1, 1.5, 0.2
assert_in_delta 10, 15, 4Asserts the exception is raised during function execution.
Returns the rescued exception, fails otherwise.
Examples
assert_raise ArithmeticError, fn ->
1 + "test"
endAsserts the exception is raised during function execution with
the expected message, which can be a Regex or an exact String.
Returns the rescued exception, fails otherwise.
Examples
assert_raise ArithmeticError, "bad argument in arithmetic expression", fn ->
1 + "test"
end
assert_raise RuntimeError, ~r/^Today's lucky number is 0.+!$/, fn ->
raise "Today's lucky number is 0.7815470541235698!"
endMacros
Asserts its argument is a truthy value.
assert instrospects the underlying expression and provide
good reporting whenever there is a failure. For example,
if the expression uses the comparison operator, the message
will show the values of the two sides. The assertion
assert 1+2+3+4 > 15will fail with the message:
Assertion with > failed
code: 1+2+3+4 > 15
lhs: 10
rhs: 15Similarly, if a match expression is given, it will report any failure in terms of that match. Given
assert [one] = [two]you’ll see:
match (=) failed
code: [one] = [two]
rhs: [2]Keep in mind that assert does not change its semantics
based on the expression. In other words, the expression
is still required to return a truthy value. For example,
the following will fail:
assert nil = some_function_that_returns_nil()Even though the match works, assert still expects a truth
value. In such cases, simply use Kernel.==/2 or
Kernel.match?/2.
Asserts a message was or is going to be received.
Unlike assert_received, it has a default timeout
of 100 milliseconds.
The expected argument is a pattern.
Examples
assert_receive :helloAsserts against a larger timeout:
assert_receive :hello, 20_000You can also match against specific patterns:
assert_receive {:hello, _}
x = 5
assert_receive {:count, ^x}Asserts a message was received and is in the current process’ mailbox. Timeout is set to 0, so there is no waiting time.
The expected argument is a pattern.
Examples
send self, :hello
assert_received :helloYou can also match against specific patterns:
send self, {:hello, "world"}
assert_received {:hello, _}Asserts expression will cause an error.
Returns the error or fails otherwise.
Examples
assert catch_error(error 1) == 1Asserts expression will exit.
Returns the exit status/message or fails otherwise.
Examples
assert catch_exit(exit 1) == 1Asserts expression will throw a value.
Returns the thrown value or fails otherwise.
Examples
assert catch_throw(throw 1) == 1A negative assertion, expects the expression to be false or nil.
Keep in mind that refute does not change the semantics of
the given expression. In other words, the following will fail:
refute {:ok, _} = some_function_that_returns_error_tuple()The code above will fail because the = operator always fails
when the sides do not match and refute/2 does not change it.
The correct way to write the refutation above is to use
Kernel.match?/2:
refute match? {:ok, _}, some_function_that_returns_error_tuple()Examples
refute age < 0Asserts message was not received (and won’t be received) within
the timeout period.
The not_expected argument is a match pattern.
Examples
refute_receive :byeRefute received with an explicit timeout:
refute_receive :bye, 1000