Implement be matcher

src/spectator/dsl/matcher_dsl.cr

@@ -14,5 +14,23 @@ module Spectator::DSL
     macro eq(expected)
       ::Spectator::Matchers::EqualityMatcher.new({{expected.stringify}}, {{expected}})
     end
+
+    # Indicates that some value should semantically equal another.
+    # The `===` operator is used for this check.
+    # This has identical behavior as a `when` condition in a `case` block.
+    #
+    # Examples:
+    # ```
+    # expect(1 + 2).to be(3)
+    # expect(5).to be(Int32) # Using `#be_a` instead is recommened here.
+    # expect(5).to be(.odd?) # Using `#be_odd` instead is recommended here.
+    # expect(tuple).to be({1, 2})
+    # ```
+    #
+    # See https://crystal-lang.org/reference/syntax_and_semantics/case.html
+    # for more examples of what could be used here.
+    macro be(expected)
+      ::Spectator::Matchers::CaseMatcher.new({{expected.stringify}}, {{expected}})
+    end
   end
 end

src/spectator/matchers/case_matcher.cr

@@ -0,0 +1,25 @@
+require "./value_matcher"
+
+module Spectator::Matchers
+  # Common matcher that tests whether two values semantically equal each other.
+  # The values are compared with the `===` operator.
+  struct CaseMatcher(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 semantically equal #{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 semantically equal #{label} (using ===)"
+    end
+  end
+end