mock provider returns errors explaining what needs to be mocked

go-runtime/ftl/call_overrider.go

@@ -1,7 +1,5 @@
 package ftl
 
-//TODO: should not be public in ftl package...
-
 import (
 	"context"
 )

go-runtime/ftl/ftltest/mock.go

@@ -2,8 +2,12 @@ package ftltest
 
 import (
 	"context"
+	"fmt"
 
 	"github.com/TBD54566975/ftl/go-runtime/ftl"
+	"github.com/TBD54566975/ftl/internal/rpc"
+
+	"github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/ftlv1connect"
 )
 
 type mockFunc func(ctx context.Context, req any) (resp any, err error)
@@ -26,9 +30,13 @@ func newMockProvider() *mockProvider {
 
 func (m *mockProvider) OverrideCall(ctx context.Context, ref ftl.Ref, req any) (override bool, resp any, err error) {
 	mock, ok := m.mocks[ref]
-	if !ok {
+	if ok {
+		resp, err = mock(ctx, req)
+		return true, resp, err
+	}
+	if rpc.IsClientAvailableInContext[ftlv1connect.VerbServiceClient](ctx) {
 		return false, nil, nil
 	}
-	resp, err = mock(ctx, req)
-	return true, resp, err
+	// Return a clean error for testing because we know the client is not available to make real calls
+	return false, nil, fmt.Errorf("no mock found")
 }

go-runtime/ftl/types.go

@@ -43,8 +43,8 @@ func (v *Ref) UnmarshalText(text []byte) error {
 	return nil
 }
 
-func (v *Ref) String() string { return v.Module + "." + v.Name }
-func (v *Ref) ToProto() *schemapb.Ref {
+func (v Ref) String() string { return v.Module + "." + v.Name }
+func (v Ref) ToProto() *schemapb.Ref {
 	return &schemapb.Ref{Module: v.Module, Name: v.Name}
 }
 

internal/rpc/context.go

@@ -180,6 +180,10 @@ func ClientFromContext[Client Pingable](ctx context.Context) Client {
 	return value.(Client) //nolint:forcetypeassert
 }
 
+func IsClientAvailableInContext[Client Pingable](ctx context.Context) bool {
+	return ctx.Value(clientKey[Client]{}) != nil
+}
+
 func propagateHeaders(ctx context.Context, isClient bool, header http.Header) (context.Context, error) {
 	if isClient {
 		if IsDirectRouted(ctx) {