Add short-hand #is and #is_not macros

These can be used for the one-liner "it" syntax.

src/spectator/dsl/example_dsl.cr

@@ -20,6 +20,23 @@ module Spectator::DSL
       ::Spectator::Expectations::ValueExpectationPartial.new({{actual.stringify}}, {{actual}})
     end
 
+    # Starts an expectation.
+    # This should be followed up with `to` or `to_not`.
+    # The value passed in will be checked
+    # to see if it satisfies the conditions specified.
+    #
+    # This method is identical to `#expect`,
+    # but is grammatically correct for the one-liner syntax.
+    # It can be used like so:
+    # ```
+    # it expects(actual).to eq(expected)
+    # ```
+    # Where the actual value is returned by the system-under-test,
+    # and the expected value is what the actual value should be to satisfy the condition.
+    macro expects(actual)
+      expect({{actual}})
+    end
+
     # Short-hand for expecting something of the subject.
     # These two are functionally equivalent:
     # ```
@@ -30,6 +47,54 @@ module Spectator::DSL
       expect(subject)
     end
 
+    # Short-hand form of `#is_expected` that can be used for one-liner syntax.
+    # For instance:
+    # ```
+    # it "is 42" do
+    #   expect(subject).to eq(42)
+    # end
+    # ```
+    # Can be shortened to:
+    # ```
+    # it is(42)
+    # ```
+    #
+    # These three are functionally equivalent:
+    # ```
+    # expect(subject).to eq("foo")
+    # is_expected.to eq("foo")
+    # is("foo")
+    # ```
+    #
+    # See also: `#is_not`
+    macro is(expected)
+      is_expected.to eq({{expected}})
+    end
+
+    # Short-hand, negated form of `#is_expected` that can be used for one-liner syntax.
+    # For instance:
+    # ```
+    # it "is not 42" do
+    #   expect(subject).to_not eq(42)
+    # end
+    # ```
+    # Can be shortened to:
+    # ```
+    # it is_not(42)
+    # ```
+    #
+    # These three are functionally equivalent:
+    # ```
+    # expect(subject).to_not eq("foo")
+    # is_expected.to_not eq("foo")
+    # is_not("foo")
+    # ```
+    #
+    # See also: `#is`
+    macro is_not(expected)
+      is_expected.to_not eq({{expected}})
+    end
+
     # Immediately fail the current test.
     # A reason can be passed,
     # which is reported in the output.