rows scan error mocking test

rows.go

@@ -8,7 +8,8 @@ import (
 )
 
 // CSVColumnParser is a function which converts trimmed csv
-// column string to a []byte representation.
+// column string to a []byte representation. currently
+// transforms NULL to nil
 var CSVColumnParser = func(s string) []byte {
 	switch {
 	case strings.ToLower(s) == "null":
@@ -54,7 +55,7 @@ type rows struct {
 	cols     []string
 	rows     [][]driver.Value
 	pos      int
-	scanErr  map[int]error
+	nextErr  map[int]error
 	closeErr error
 }
 
@@ -77,14 +78,14 @@ func (r *rows) Next(dest []driver.Value) error {
 		dest[i] = col
 	}
 
-	return r.scanErr[r.pos-1]
+	return r.nextErr[r.pos-1]
 }
 
 // NewRows allows Rows to be created from a
 // sql driver.Value slice or from the CSV string and
 // to be used as sql driver.Rows
 func NewRows(columns []string) Rows {
-	return &rows{cols: columns, scanErr: make(map[int]error)}
+	return &rows{cols: columns, nextErr: make(map[int]error)}
 }
 
 func (r *rows) CloseError(err error) Rows {
@@ -93,7 +94,7 @@ func (r *rows) CloseError(err error) Rows {
 }
 
 func (r *rows) RowError(row int, err error) Rows {
-	r.scanErr[row] = err
+	r.nextErr[row] = err
 	return r
 }
 

rows_test.go

@@ -180,10 +180,7 @@ func TestQuerySingleRow(t *testing.T) {
 	}
 }
 
-// @TODO: the only way to mock columns error would be
-// to return nil instead of rows, but rows.Close will
-// panic due to a bug in go sql package
-func TODO_TestRowsColumnsError(t *testing.T) {
+func TestRowsScanError(t *testing.T) {
 	t.Parallel()
 	db, mock, err := New()
 	if err != nil {
@@ -191,16 +188,27 @@ func TODO_TestRowsColumnsError(t *testing.T) {
 	}
 	defer db.Close()
 
-	mock.ExpectQuery("SELECT").WillReturnRows(nil)
+	r := NewRows([]string{"col1", "col2"}).AddRow("one", "two").AddRow("one", nil)
+	mock.ExpectQuery("SELECT").WillReturnRows(r)
 
 	rs, err := db.Query("SELECT")
 	if err != nil {
 		t.Fatalf("unexpected error: %s", err)
 	}
+	defer rs.Close()
 
-	_, err = rs.Columns()
+	var one, two string
+	if !rs.Next() || rs.Err() != nil || rs.Scan(&one, &two) != nil {
+		t.Fatal("unexpected error on first row scan")
+	}
+
+	if !rs.Next() || rs.Err() != nil {
+		t.Fatal("unexpected error on second row read")
+	}
+
+	err = rs.Scan(&one, &two)
 	if err == nil {
-		t.Fatal("expected an error for columns")
+		t.Fatal("expected an error for scan, but got none")
 	}
 
 	if err := mock.ExpectationsWereMet(); err != nil {

sqlmock.go

@@ -201,7 +201,6 @@ func (c *Sqlmock) Query(query string, args []driver.Value) (rw driver.Rows, err
 		return nil, t.err // mocked to return error
 	}
 
-	// remove when rows_test.go:186 is available, won't cause a BC
 	if t.rows == nil {
 		return nil, fmt.Errorf("query '%s' with args %+v, must return a database/sql/driver.rows, but it was not set for expectation %T as %+v", query, args, t, t)
 	}