assert_difference(expression, difference = 1, message = nil, &block)
Instance Public methods
Test numeric difference between the return value of an expression as a result of what is evaluated in the yielded block.
1 2 3 | assert_difference 'Article.count' do post :create, article: {...}end |
An arbitrary expression is passed in and evaluated.
1 2 3 | assert_difference 'assigns(:article).comments(:reload).size' do post :create, comment: {...}end |
An arbitrary positive or negative difference can be specified. The default
is 1.
1 2 3 | assert_difference 'Article.count', -1 do post :delete, id: ...end |
An array of expressions can also be passed in and evaluated.
1 2 3 | assert_difference [ 'Article.count', 'Post.count' ], 2 do post :create, article: {...}end |
A lambda or a list of lambdas can be passed in and evaluated:
1 2 3 4 5 6 7 | assert_difference ->{ Article.count }, 2 do post :create, article: {...}endassert_difference [->{ Article.count }, ->{ Post.count }], 2 do post :create, article: {...}end |
An error message can be specified.
1 2 3 | assert_difference 'Article.count', -1, 'An Article should be destroyed' do post :delete, id: ...end |
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