database/sql: fix TestConversions when count > 1

Provide a fresh conversion table for TestConversions as it gets
modified on each test.

Change-Id: I6e2240d0c3455451271a6879e994b82222c3d44c
Reviewed-on: https://go-review.googlesource.com/89595
Run-TryBot: Daniel Theophanes <kardianos@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

src/database/sql/convert_test.go

@@ -64,7 +64,9 @@ var (
 	scaniface  interface{}
 )
 
-var conversionTests = []conversionTest{
+func conversionTests() []conversionTest {
+	// Return a fresh instance to test so "go test -count 2" works correctly.
+	return []conversionTest{
 		// Exact conversions (destination pointer type matches source type)
 		{s: "foo", d: &scanstr, wantstr: "foo"},
 		{s: 123, d: &scanint, wantint: 123},
@@ -183,6 +185,7 @@ var conversionTests = []conversionTest{
 
 		// Other errors
 		{s: complex(1, 2), d: &scanstr, wanterr: `unsupported Scan, storing driver.Value type complex128 into type *string`},
+	}
 }
 
 func intPtrValue(intptr interface{}) interface{} {
@@ -210,7 +213,7 @@ func timeValue(ptr interface{}) time.Time {
 }
 
 func TestConversions(t *testing.T) {
-	for n, ct := range conversionTests {
+	for n, ct := range conversionTests() {
 		err := convertAssign(ct.d, ct.s)
 		errstr := ""
 		if err != nil {