Take a look at the docs here:
http://apidock.com/rails/ActionController/Assertions/SelectorAssertions/assert_select
From the docs:
assert_select is an assertion that selects elements and makes one or more equality tests.
and from the equality tests sections:
The equality test may be one of the following:
true – Assertion is true if at least one element selected.
false – Assertion is true if no element selected.
String/Regexp – Assertion is true if the text value of at least one
element matches the string or regular expression.Integer – Assertion is true if exactly that number of elements are
selected.Range – Assertion is true if the number of selected elements fit the
range.If no equality test specified, the assertion is true if at least one
element selected.
And a simple example:
# Page contains no forms
assert_select "form", false, "This page must contain no forms"