Use Equal as a default matcher for string contents

matchers/be_a_file_matching.go

@@ -4,17 +4,19 @@ import (
 	"fmt"
 	"os"
 
+	"github.com/onsi/gomega"
 	"github.com/onsi/gomega/types"
 )
 
 type BeAFileMatchingMatcher struct {
+	expected        interface{}
 	expectedMatcher types.GomegaMatcher
 	contents        string
 }
 
-func BeAFileMatching(expectedMatcher types.GomegaMatcher) *BeAFileMatchingMatcher {
+func BeAFileMatching(expected interface{}) *BeAFileMatchingMatcher {
 	return &BeAFileMatchingMatcher{
-		expectedMatcher: expectedMatcher,
+		expected: expected,
 	}
 }
 
@@ -26,6 +28,14 @@ func (matcher *BeAFileMatchingMatcher) Match(actual interface{}) (success bool,
 		return false, fmt.Errorf("BeAFileMatchingMatcher expects a file path")
 	}
 
+	if expectedString, ok := matcher.expected.(string); ok {
+		matcher.expectedMatcher = gomega.Equal(expectedString)
+	} else {
+		if matcher.expectedMatcher, ok = matcher.expected.(types.GomegaMatcher); !ok {
+			return false, fmt.Errorf("BeAFileMatching expects a string or a types.GomegaMatcher")
+		}
+	}
+
 	bytes, err := os.ReadFile(actualFilename)
 	if err != nil {
 		return false, err

matchers/be_a_file_matching_test.go

@@ -24,6 +24,24 @@ func testBeAFileMatching(t *testing.T, context spec.G, it spec.S) {
 		Expect(os.WriteFile(filename, []byte("hello world"), os.ModePerm)).To(Succeed())
 	})
 
+	context("uses Equal by default", func() {
+		it("will pass", func() {
+			matcher = matchers.BeAFileMatching("hello world")
+
+			match, err := matcher.Match(filename)
+			Expect(match).To(Equal(true))
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		it("will fail", func() {
+			matcher = matchers.BeAFileMatching("foobar")
+
+			match, err := matcher.Match(filename)
+			Expect(match).To(Equal(false))
+			Expect(err).NotTo(HaveOccurred())
+		})
+	})
+
 	context("will wrap ContainsSubstring", func() {
 		it("will pass", func() {
 			matcher = matchers.BeAFileMatching(ContainSubstring("hello"))
@@ -120,6 +138,14 @@ func testBeAFileMatching(t *testing.T, context spec.G, it spec.S) {
 	})
 
 	context("failure cases", func() {
+		context("BeAFileMatching is called with a non-string and non-types.GomegaMatcher", func() {
+			it("will return an error", func() {
+				matcher = matchers.BeAFileMatching(42)
+				_, err := matcher.Match(filename)
+				Expect(err).To(MatchError("BeAFileMatching expects a string or a types.GomegaMatcher"))
+			})
+		})
+
 		context("Match is called with a non-string", func() {
 			it("will return an error", func() {
 				matcher = matchers.BeAFileMatching(ContainSubstring(""))