Add RSpec contain_exactly matcher spec

spec/rspec/expectations/contain_exactly_matcher_spec.cr

@@ -0,0 +1,32 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/contain-exactly-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`contain_exactly` matcher" do
+  context "Array is expected to contain every value" do
+    describe [1, 2, 3] do
+      it { is_expected.to contain_exactly(1, 2, 3) }
+      it { is_expected.to contain_exactly(1, 3, 2) }
+      it { is_expected.to contain_exactly(2, 1, 3) }
+      it { is_expected.to contain_exactly(2, 3, 1) }
+      it { is_expected.to contain_exactly(3, 1, 2) }
+      it { is_expected.to contain_exactly(3, 2, 1) }
+
+      # deliberate failures
+      # TODO: Add support for expected failures.
+      xit { is_expected.to contain_exactly(1, 2, 1) }
+    end
+  end
+
+  context "Array is not expected to contain every value" do
+    describe [1, 2, 3] do
+      it { is_expected.to_not contain_exactly(1, 2, 3, 4) }
+      it { is_expected.to_not contain_exactly(1, 2) }
+
+      # deliberate failures
+      # TODO: Add support for expected failures.
+      xit { is_expected.to_not contain_exactly(1, 3, 2) }
+    end
+  end
+end