assert: improve EqualValues test coverage to 100%

Extend TestNotEqualValues to also test EqualValues by leveraging the fact
that they are inverse functions. The same test cases are used to verify
that EqualValues returns the opposite result of NotEqualValues.

This change ensures both success and failure paths are tested for
EqualValues, covering the error formatting and failure reporting code
that was previously untested.

Coverage improvement:
- EqualValues: 57.1% → 100.0%
- Overall package: 68.4% → 68.5%

The test function was renamed to TestEqualValuesAndNotEqualValues to
reflect its dual purpose while maintaining all existing test logic.

Co-Authored-By: sketch <hello@sketch.dev>
Change-ID: s30d4192b08186d88k

Author: dolmen

assert/assertions_test.go

@@ -978,15 +978,15 @@ func TestNotEqual(t *testing.T) {
 	}
 }
 
-func TestNotEqualValues(t *testing.T) {
+func TestEqualValuesAndNotEqualValues(t *testing.T) {
 	t.Parallel()
 
 	mockT := new(testing.T)
 
 	cases := []struct {
-		expected interface{}
-		actual   interface{}
-		result   bool
+		expected       interface{}
+		actual         interface{}
+		notEqualResult bool // result for NotEqualValues
 	}{
 		// cases that are expected not to match
 		{"Hello World", "Hello World!", true},
@@ -1013,11 +1013,22 @@ func TestNotEqualValues(t *testing.T) {
 	}
 
 	for _, c := range cases {
+		// Test NotEqualValues
 		t.Run(fmt.Sprintf("NotEqualValues(%#v, %#v)", c.expected, c.actual), func(t *testing.T) {
 			res := NotEqualValues(mockT, c.expected, c.actual)
 
-			if res != c.result {
-				t.Errorf("NotEqualValues(%#v, %#v) should return %#v", c.expected, c.actual, c.result)
+			if res != c.notEqualResult {
+				t.Errorf("NotEqualValues(%#v, %#v) should return %#v", c.expected, c.actual, c.notEqualResult)
+			}
+		})
+
+		// Test EqualValues (inverse of NotEqualValues)
+		t.Run(fmt.Sprintf("EqualValues(%#v, %#v)", c.expected, c.actual), func(t *testing.T) {
+			expectedEqualResult := !c.notEqualResult // EqualValues should return opposite of NotEqualValues
+			res := EqualValues(mockT, c.expected, c.actual)
+
+			if res != expectedEqualResult {
+				t.Errorf("EqualValues(%#v, %#v) should return %#v", c.expected, c.actual, expectedEqualResult)
 			}
 		})
 	}