Add tests for equality matcher

spec/matchers/equality_matcher_spec.cr

@@ -0,0 +1,32 @@
+require "../spec_helper"
+
+Spectator.describe "eq matcher" do
+  it "is true for equal values" do
+    expect(42).to eq(42)
+  end
+
+  it "is false for inequal values" do
+    expect(42).to_not eq(24)
+  end
+
+  it "is true for identical references" do
+    string = "foobar"
+    expect(string).to eq(string)
+  end
+
+  it "is false for different references" do
+    string1 = "foo"
+    string2 = "bar"
+    expect(string1).to_not eq(string2)
+  end
+
+  double(:fake) do
+    stub instance.==(other) { true }
+  end
+
+  it "uses the == operator" do
+    dbl = double(:fake)
+    expect(42).to eq(dbl)
+    expect(dbl).to have_received(:==).with(42).once
+  end
+end