Implement `match` (regex) matcher

src/spectator/dsl/matcher_dsl.cr

@@ -43,5 +43,19 @@ module Spectator::DSL
     macro be_a(expected)
       ::Spectator::Matchers::TypeMatcher({{expected}}).new
     end
+
+    # Indicates that some value should match another.
+    # The `=~` operator is used for this check.
+    # Typically a regular expression is used,
+    # but any type that has the `=~` operator will work.
+    #
+    # Examples:
+    # ```
+    # expect("foo").to match(/foo|bar/)
+    # expect("BAR").to match(/foo|bar/i)
+    # ```
+    macro match(expected)
+      ::Spectator::Matchers::RegexMatcher.new({{expected.stringify}}, {{expected}})
+    end
   end
 end

src/spectator/matchers/regex_matcher.cr

@@ -0,0 +1,25 @@
+require "./value_matcher"
+
+module Spectator::Matchers
+  # Matcher that tests whether a value matches a regular expression.
+  # The value is compared with the `=~` operator.
+  struct RegexMatcher(ExpectedType) < ValueMatcher(ExpectedType)
+    # Determines whether the matcher is satisfied with the value given to it.
+    # True is returned if the match was successful, false otherwise.
+    def match?(partial : Expectations::ValueExpectationPartial(ActualType)) : Bool forall ActualType
+      !!(partial.actual =~ expected)
+    end
+
+    # Describes the condition that satisfies the matcher.
+    # This is informational and displayed to the end-user.
+    def message(partial : Expectations::ValueExpectationPartial(ActualType)) : String forall ActualType
+      "Expected #{partial.label} to match #{label} (using =~)"
+    end
+
+    # Describes the condition that won't satsify the matcher.
+    # This is informational and displayed to the end-user.
+    def negated_message(partial : Expectations::ValueExpectationPartial(ActualType)) : String forall ActualType
+      "Expected #{partial.label} to not match #{label} (using =~)"
+    end
+  end
+end