Add RSpec be matchers spec

spec/rspec/expectations/be_matchers_spec.cr

@@ -0,0 +1,70 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/be-matchers
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`be` matchers" do
+  context "be_truthy matcher" do
+    specify { expect(true).to be_truthy }
+    specify { expect(7).to be_truthy }
+    specify { expect("foo").to be_truthy }
+    specify { expect(nil).not_to be_truthy }
+    specify { expect(false).not_to be_truthy }
+
+    # deliberate failures
+    # TODO: Add support for expected failures.
+    pending { expect(true).not_to be_truthy }
+    pending { expect(7).not_to be_truthy }
+    pending { expect("foo").not_to be_truthy }
+    pending { expect(nil).to be_truthy }
+    pending { expect(false).to be_truthy }
+  end
+
+  context "be_falsey matcher" do
+    specify { expect(nil).to be_falsey }
+    specify { expect(false).to be_falsey }
+    specify { expect(true).not_to be_falsey }
+    specify { expect(7).not_to be_falsey }
+    specify { expect("foo").not_to be_falsey }
+
+    # deliberate failures
+    # TODO: Add support for expected failures.
+    pending { expect(nil).not_to be_falsey }
+    pending { expect(false).not_to be_falsey }
+    pending { expect(true).to be_falsey }
+    pending { expect(7).to be_falsey }
+    pending { expect("foo").to be_falsey }
+  end
+
+  context "be_nil matcher" do
+    specify { expect(nil).to be_nil }
+    specify { expect(false).not_to be_nil }
+    specify { expect(true).not_to be_nil }
+    specify { expect(7).not_to be_nil }
+    specify { expect("foo").not_to be_nil }
+
+    # deliberate failures
+    # TODO: Add support for expected failures.
+    pending { expect(nil).not_to be_nil }
+    pending { expect(false).to be_nil }
+    pending { expect(true).to be_nil }
+    pending { expect(7).to be_nil }
+    pending { expect("foo").to be_nil }
+  end
+
+  context "be matcher" do
+    specify { expect(true).to be }
+    specify { expect(7).to be }
+    specify { expect("foo").to be }
+    specify { expect(nil).not_to be }
+    specify { expect(false).not_to be }
+
+    # deliberate failures
+    # TODO: Add support for expected failures.
+    pending { expect(true).not_to be }
+    pending { expect(7).not_to be }
+    pending { expect("foo").not_to be }
+    pending { expect(nil).to be }
+    pending { expect(false).to be }
+  end
+end