Improve Read tests for paster

handler/paste/paster_test.go

@@ -1,10 +1,12 @@
 package paste
 
 import (
+	"io"
 	"testing"
 
 	"github.com/google/uuid"
 	"github.com/ollien/updown/repository"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/mock"
 )
 
@@ -53,15 +55,23 @@ func TestRead(t *testing.T) {
 	paster := setupPaster()
 	mockFile := paster.file.(*MockFile)
 
-	buffer := make([]byte, 5)
-	mockFile.On("Read", buffer).Return(len(buffer), nil).Once()
+	pasteContents := "hello"
+	readBuffer := make([]byte, len(pasteContents))
+	mockFile.On("Read", readBuffer).Return(len(readBuffer), io.EOF).Run(func(args mock.Arguments) {
+		buffer := args.Get(0).([]byte)
+		// Dump pasteContents into the buffer
+		for i, char := range pasteContents {
+			buffer[i] = byte(char)
+		}
+	}).Once()
 	// Ensure we seek to the start of the file
 	mockFile.On("Seek", int64(0), 0).Return(int64(0), nil).Once()
 	mockFile.AssertNotCalled(t, "Close")
 	mockFile.AssertNotCalled(t, "Write")
 
-	paster.Read(buffer)
+	paster.Read(readBuffer)
 	mockFile.AssertExpectations(t)
+	assert.Equal(t, pasteContents, string(readBuffer))
 }
 
 func TestWrite(t *testing.T) {