Add some database tests to improve coverage

database/driver_test.go

@@ -1,8 +1,95 @@
 package database
 
+import (
+	"io"
+	"testing"
+)
+
 func ExampleDriver() {
 	// see database/stub for an example
 
 	// database/stub/stub.go has the driver implementation
 	// database/stub/stub_test.go runs database/testing/test.go:Test
 }
+
+// Using database/stub here is not possible as it
+// results in an import cycle.
+type mockDriver struct {
+	url string
+}
+
+func (m *mockDriver) Open(url string) (Driver, error) {
+	return &mockDriver{
+		url: url,
+	}, nil
+}
+
+func (m *mockDriver) Close() error {
+	return nil
+}
+
+func (m *mockDriver) Lock() error {
+	return nil
+}
+
+func (m *mockDriver) Unlock() error {
+	return nil
+}
+
+func (m *mockDriver) Run(migration io.Reader) error {
+	return nil
+}
+
+func (m *mockDriver) SetVersion(version int, dirty bool) error {
+	return nil
+}
+
+func (m *mockDriver) Version() (version int, dirty bool, err error) {
+	return 0, false, nil
+}
+
+func (m *mockDriver) Drop() error {
+	return nil
+}
+
+func TestRegisterTwice(t *testing.T) {
+	Register("mock", &mockDriver{})
+
+	var err interface{}
+	func() {
+		defer func() {
+			err = recover()
+		}()
+		Register("mock", &mockDriver{})
+	}()
+
+	if err == nil {
+		t.Fatal("expected a panic when calling Register twice")
+	}
+}
+
+func TestOpen(t *testing.T) {
+	// Make sure the driver is registered.
+	// But if the previous test already registered it just ignore the panic.
+	// If we don't do this it will be impossible to run this test standalone.
+	func() {
+		defer func() {
+			_ = recover()
+		}()
+		Register("mock", &mockDriver{})
+	}()
+
+	u := "mock://user:pass@tcp(host:1337)/db"
+
+	if d, err := Open(u); err != nil {
+		t.Fatalf("did not expect %q", err)
+	} else if md, ok := d.(*mockDriver); !ok {
+		t.Fatalf("expected *stub.Stub got %T", d)
+	} else if md.url != u {
+		t.Fatalf("expected %q got %q", u, md.url)
+	}
+
+	if _, err := Open("unknown://bla"); err == nil {
+		t.Fatal("expected an error for an unknown driver")
+	}
+}