Add support for be === and be =~

Addresses https://github.com/icy-arctic-fox/spectator/issues/26

src/spectator/matchers/pattern_matcher.cr

@@ -0,0 +1,41 @@
+require "./value_matcher"
+
+module Spectator::Matchers
+  # Common matcher that tests whether a value matches another.
+  # The values are compared with the === operator.
+  # This is the same as `CaseMatcher`, but the operands are flipped.
+  struct PatternMatcher(ExpectedType) < ValueMatcher(ExpectedType)
+    # Short text about the matcher's purpose.
+    # This explains what condition satisfies the matcher.
+    # The description is used when the one-liner syntax is used.
+    def description : String
+      "matches #{expected.label}"
+    end
+
+    # Checks whether the matcher is satisifed with the expression given to it.
+    private def match?(actual : TestExpression(T)) : Bool forall T
+      actual.value === expected.value
+    end
+
+    # Message displayed when the matcher isn't satisifed.
+    #
+    # This is only called when `#match?` returns false.
+    #
+    # The message should typically only contain the test expression labels.
+    # Actual values should be returned by `#values`.
+    private def failure_message(actual) : String
+      "#{actual.label} does not match #{expected.label}"
+    end
+
+    # Message displayed when the matcher isn't satisifed and is negated.
+    # This is essentially what would satisfy the matcher if it wasn't negated.
+    #
+    # This is only called when `#does_not_match?` returns false.
+    #
+    # The message should typically only contain the test expression labels.
+    # Actual values should be returned by `#values`.
+    private def failure_message_when_negated(actual) : String
+      "#{actual.label} matched #{expected.label}"
+    end
+  end
+end

src/spectator/matchers/truthy_matcher.cr

@@ -82,6 +82,26 @@ module Spectator::Matchers
       InequalityMatcher.new(expected)
     end
 
+    # Creates a matcher that checks if a value is semantically equal to an expected value.
+    # The spec would look like:
+    # ```
+    # expect("foobar").to be === /foo/
+    # ```
+    def ===(value)
+      expected = TestValue.new(value)
+      PatternMatcher.new(expected)
+    end
+
+    # Creates a matcher that checks if a value matches the pattern of an expected value.
+    # The spec would look like:
+    # ```
+    # expect("foobar").to be =~ /foo/
+    # ```
+    def =~(value)
+      expected = TestValue.new(value)
+      PatternMatcher.new(expected)
+    end
+
     # Checks whether the matcher is satisifed with the expression given to it.
     private def match?(actual : TestExpression(T)) : Bool forall T
       @truthy == !!actual.value