mock Prepare to return error

connection.go

@@ -85,6 +85,22 @@ func (c *conn) Exec(query string, args []driver.Value) (res driver.Result, err e
 }
 
 func (c *conn) Prepare(query string) (driver.Stmt, error) {
+	e := c.next()
+
+	// for backwards compatibility, ignore when Prepare not expected
+	if e == nil {
+		return &statement{mock.conn, stripQuery(query)}, nil
+	}
+	eq, ok := e.(*expectedPrepare)
+	if !ok {
+		return &statement{mock.conn, stripQuery(query)}, nil
+	}
+
+	eq.triggered = true
+	if eq.err != nil {
+		return nil, eq.err // mocked to return error
+	}
+
 	return &statement{mock.conn, stripQuery(query)}, nil
 }
 

expectations.go

@@ -117,3 +117,10 @@ type expectedExec struct {
 
 	result driver.Result
 }
+
+// Prepare expectation
+type expectedPrepare struct {
+	commonExpectation
+
+	statement driver.Stmt
+}

sqlmock.go

@@ -122,6 +122,14 @@ func ExpectRollback() Mock {
 	return mock.conn
 }
 
+// ExpectPrepare expects Query to be prepared
+func ExpectPrepare() Mock {
+	e := &expectedPrepare{}
+	mock.conn.expectations = append(mock.conn.expectations, e)
+	mock.conn.active = e
+	return mock.conn
+}
+
 // WillReturnError the expectation will return an error
 func (c *conn) WillReturnError(err error) Mock {
 	c.active.setError(err)