库： rspec/rspec-expectations matcher匹配器常用

https://github.com/rspec/rspec-expectations

https://relishapp.com/rspec/rspec-expectations/v/3-7/docs

总文档连接：

RSpec.info/documentation/

be_completed是Predicate matchers

expect(actual).to be_xxx  #passes if actual.xxx?

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RSpec::Expectations lets you express expected outcomes on an object in an example.

Built-in matchers

expect(actual_value).to eq(expected_value)

expect(actual_value).to be >= expected_value   包括>, < , <=, >=

expect(actual_value).to match(/expression/)  正则表达式(expect不支持匹配符号 =~)

expect(array).to all(inner_matcher)    #让array通过inner_matcher

如：expect([1,2,3]).to all(be_truthy)

expect(array).to contain_exactly(expected_array) #如果实际的和期待的数组包含相同的元素，则期待成功。不考虑顺序。

contain_exactly等同于match_array

expect(actual).to exist

Collection membership

expect(actual).to include(expected)  #actual可以是数组，字符串，hash.

例子：expect([1,2,3]).to include(1,2), expect({:a => "b"}).to include(:a => "b")

include的变型， start_with, end_with

Types/classes

expect(actual).to be_an_instance_of(expected)

# passes if actual.class == expected

expect(actual).to be_a(expected)  #passes if actual.kind_of?(expected)

Predicate matchers 

expect(actual).to be_xxx   #passes if actual.xxx?

expect(actual).to have_xxx(:arg) #passes if actual.has_xxx?(:arg)

expect(actual).to have_attributes(key/value pairs)

Truthiness

expect(actual).to be_truthy/falsy     # passes if actual is truthy (not nil or false)

expect(actual).to be true/false  #passes if actual == true/false

expect(actual).to be_nil   #passes if actual is nil

expect(actual).to_not be_nil   #passes if actual is not nil

Ranges

expect(1..10).to cover(3)

expect(actual).to be_between(min, max)

Expecting errors

expect { ... }.to raise_error
expect { ... }.to raise_error(ErrorClass)
expect { ... }.to raise_error("message")
expect { ... }.to raise_error(ErrorClass, "message")

expect可以用于block也可以用于value expectations.

Expecting throws and Yielding没看懂⚠️

Compound Matcher Expressions

通过user，or可以创建混合匹配表达式 。

expect(stoplight.color).to eq("red").or eq("green").or eq("yellow")

expect(alphabet).to start_with("a").and end_with("z")

Composing Matchers

以下matchers接受matchers 作为参数。

• change().by(matcher) #改变sth等于by(匹配的值)
• change{}.from(mather).to(matcher) #改变sth,从matcher_val到mather_val
• include(matcher, matcher)
• include(:key => matcher, :other => mathcer)

 等等：详细见https://relishapp.com/rspec/rspec-expectations/v/3-7/docs/composing-matchers

‘change’ matcher:

• expect {do_sth}.to change(object, :attribute)
• expect {do_sth}.to change{object.attribute}
• 可以联合  from().to();  by(), by_at_least(), by_at_most()

Relish(n:great enjoyment; 水果蔬菜酱) 案例连接