diff --git a/previewProviderUpgrade.go b/previewProviderUpgrade.go
index 88bf16b..ff50ead 100644
--- a/previewProviderUpgrade.go
+++ b/previewProviderUpgrade.go
@@ -32,12 +32,23 @@ func PreviewProviderUpgrade(pulumiTest *pulumitest.PulumiTest, providerName stri
 			test.T().Logf("writing grpc log to %s", grpcLogPath)
 			grptLog.WriteTo(grpcLogPath)
 		},
-		optrun.WithOpts(opttest.NewStackOptions(optnewstack.EnableAutoDestroy())),
 		optrun.WithCache(filepath.Join(cacheDir, "stack.json")),
-		optrun.WithOpts(options.BaselineOpts...))
+		optrun.WithOpts(
+			opttest.NewStackOptions(optnewstack.EnableAutoDestroy()),
+			baselineProviderOpt(options, providerName, baselineVersion)),
+		optrun.WithOpts(options.BaselineOpts...),
+	)
 	return previewTest.Preview()
 }
 
+func baselineProviderOpt(options optproviderupgrade.PreviewProviderUpgradeOptions, providerName string, baselineVersion string) opttest.Option {
+	if options.DisableAttach {
+		return opttest.DownloadProviderVersion(providerName, baselineVersion)
+	} else {
+		return opttest.AttachDownloadedPlugin(providerName, baselineVersion)
+	}
+}
+
 func getCacheDir(options optproviderupgrade.PreviewProviderUpgradeOptions, programName string, baselineVersion string) string {
 	var cacheDir string
 	for _, pathTemplateElement := range options.CacheDirTemplate {
diff --git a/providers/providerInterceptProxy.go b/providers/providerInterceptProxy.go
index 85e7a28..c53687b 100644
--- a/providers/providerInterceptProxy.go
+++ b/providers/providerInterceptProxy.go
@@ -57,7 +57,8 @@ func NewProviderInterceptProxy(ctx context.Context, downstreamProviderPort Port,
 		fmt.Sprintf("127.0.0.1:%d", downstreamProviderPort),
 		grpc.WithTransportCredentials(insecure.NewCredentials()),
 		grpc.WithUnaryInterceptor(rpcutil.OpenTracingClientInterceptor()),
-		grpc.WithStreamInterceptor(rpcutil.OpenTracingStreamClientInterceptor()))
+		grpc.WithStreamInterceptor(rpcutil.OpenTracingStreamClientInterceptor()),
+		grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(1024*1024*400)))
 	if err != nil {
 		return nil, err
 	}
diff --git a/providers/providerInterceptProxy_test.go b/providers/providerInterceptProxy_test.go
index 0efddb9..be42746 100644
--- a/providers/providerInterceptProxy_test.go
+++ b/providers/providerInterceptProxy_test.go
@@ -10,6 +10,7 @@ import (
 	"github.com/pulumi/providertest/pulumitest/opttest"
 	pulumirpc "github.com/pulumi/pulumi/sdk/v3/proto/go"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 	"google.golang.org/protobuf/types/known/emptypb"
 )
 
@@ -17,26 +18,29 @@ func TestProviderInterceptProxy(t *testing.T) {
 	t.Parallel()
 	ctx, cancel := context.WithCancel(context.Background())
 	t.Cleanup(cancel)
-	var didAttach, didForward bool
-	mockFactory := providers.ProviderMockFactory(ctx, providers.ProviderMocks{
-		Attach: func(ctx context.Context, in *pulumirpc.PluginAttach) (*emptypb.Empty, error) {
-			didForward = true
-			return &emptypb.Empty{}, nil
-		},
-		Create: func(ctx context.Context, in *pulumirpc.CreateRequest) (*pulumirpc.CreateResponse, error) {
-			// Return without error to indicate success.
-			return &pulumirpc.CreateResponse{}, nil
-		},
-	})
-	interceptedFactory := providers.ProviderInterceptFactory(ctx, mockFactory, providers.ProviderInterceptors{
+	var didAttach bool
+	// Ensure plugin is downloaded so YAML can look up its schema
+	_, err := providers.DownloadPluginBinary("azure-native", "2.10.0")
+	require.NoError(t, err)
+
+	interceptedFactory := providers.ProviderInterceptFactory(ctx, providers.DownloadPluginBinaryFactory("azure-native", "2.10.0"), providers.ProviderInterceptors{
 		Attach: func(ctx context.Context, in *pulumirpc.PluginAttach, client pulumirpc.ResourceProviderClient) (*emptypb.Empty, error) {
 			didAttach = true
 			return client.Attach(ctx, in)
 		},
+		Configure: func(ctx context.Context, in *pulumirpc.ConfigureRequest, client pulumirpc.ResourceProviderClient) (*pulumirpc.ConfigureResponse, error) {
+			// Skip checking the real configuration
+			return &pulumirpc.ConfigureResponse{}, nil
+		},
+		Check: func(ctx context.Context, in *pulumirpc.CheckRequest, client pulumirpc.ResourceProviderClient) (*pulumirpc.CheckResponse, error) {
+			// Skip checking the real configuration
+			return &pulumirpc.CheckResponse{Inputs: in.News}, nil
+		},
 	})
-	test := pulumitest.NewPulumiTest(t, filepath.Join("..", "pulumitest", "testdata", "yaml_program"), opttest.AttachProvider("random", interceptedFactory))
+	test := pulumitest.NewPulumiTest(t,
+		filepath.Join("..", "pulumitest", "testdata", "yaml_azure"),
+		opttest.AttachProvider("azure-native", interceptedFactory))
 
 	test.Preview()
 	assert.True(t, didAttach, "expected Attach to be called in proxy")
-	assert.True(t, didForward, "expected Attach to be called in downstream provider")
 }
diff --git a/providers/providerMock.go b/providers/providerMock.go
index adedd9a..f00dc51 100644
--- a/providers/providerMock.go
+++ b/providers/providerMock.go
@@ -36,14 +36,14 @@ type ProviderMocks struct {
 }
 
 // ProviderInterceptFactory creates a new provider factory that can be used to intercept calls to a downstream provider.
-func ProviderMockFactory(ctx context.Context, mocks ProviderMocks) ProviderFactory {
+func ProviderMockFactory(mocks ProviderMocks) ProviderFactory {
 	return ResourceProviderFactory(func() (rpc.ResourceProviderServer, error) {
-		return NewProviderMock(ctx, mocks)
+		return NewProviderMock(mocks)
 	})
 }
 
 // NewProviderMock creates a new provider proxy that can be used to intercept calls to a downstream provider.
-func NewProviderMock(ctx context.Context, mocks ProviderMocks) (rpc.ResourceProviderServer, error) {
+func NewProviderMock(mocks ProviderMocks) (rpc.ResourceProviderServer, error) {
 	return &providerMock{
 		mocks: mocks,
 	}, nil
@@ -92,12 +92,7 @@ func (i *providerMock) Configure(ctx context.Context, in *rpc.ConfigureRequest)
 	if i.mocks.Configure != nil {
 		return i.mocks.Configure(ctx, in)
 	}
-	return &rpc.ConfigureResponse{
-		AcceptSecrets:   true,
-		SupportsPreview: true,
-		AcceptResources: true,
-		AcceptOutputs:   true,
-	}, nil
+	return &rpc.ConfigureResponse{}, nil
 }
 
 func (i *providerMock) Construct(ctx context.Context, in *rpc.ConstructRequest) (*rpc.ConstructResponse, error) {
diff --git a/providers/providerMock_test.go b/providers/providerMock_test.go
new file mode 100644
index 0000000..6172f91
--- /dev/null
+++ b/providers/providerMock_test.go
@@ -0,0 +1,71 @@
+package providers_test
+
+import (
+	"context"
+	"path/filepath"
+	"testing"
+
+	"github.com/pulumi/providertest/providers"
+	"github.com/pulumi/providertest/pulumitest"
+	"github.com/pulumi/providertest/pulumitest/opttest"
+	pulumirpc "github.com/pulumi/pulumi/sdk/v3/proto/go"
+	"github.com/stretchr/testify/assert"
+	"google.golang.org/protobuf/types/known/emptypb"
+	"google.golang.org/protobuf/types/known/structpb"
+)
+
+func TestProviderMock(t *testing.T) {
+	t.Parallel()
+	source := filepath.Join("..", "pulumitest", "testdata", "python_gcp")
+
+	t.Run("defaults", func(t *testing.T) {
+		test := pulumitest.NewPulumiTest(t, source,
+			opttest.AttachProvider("gcp",
+				providers.ProviderMockFactory(providers.ProviderMocks{})))
+		test.Preview()
+	})
+
+	t.Run("with mocks", func(t *testing.T) {
+		var attached, configured, checkedConfig, checked, created bool
+		test := pulumitest.NewPulumiTest(t, source,
+			opttest.AttachProvider("gcp",
+				providers.ProviderMockFactory(providers.ProviderMocks{
+					Attach: func(ctx context.Context, in *pulumirpc.PluginAttach) (*emptypb.Empty, error) {
+						attached = true
+						return &emptypb.Empty{}, nil
+					},
+					Configure: func(ctx context.Context, in *pulumirpc.ConfigureRequest) (*pulumirpc.ConfigureResponse, error) {
+						configured = true
+						return &pulumirpc.ConfigureResponse{}, nil
+					},
+					CheckConfig: func(ctx context.Context, in *pulumirpc.CheckRequest) (*pulumirpc.CheckResponse, error) {
+						checkedConfig = true
+						return &pulumirpc.CheckResponse{}, nil
+					},
+					Check: func(ctx context.Context, in *pulumirpc.CheckRequest) (*pulumirpc.CheckResponse, error) {
+						checked = true
+						return &pulumirpc.CheckResponse{Inputs: in.News}, nil
+					},
+					Create: func(ctx context.Context, in *pulumirpc.CreateRequest) (*pulumirpc.CreateResponse, error) {
+						created = true
+						return &pulumirpc.CreateResponse{Id: "fake-id", Properties: &structpb.Struct{
+							Fields: map[string]*structpb.Value{
+								"url": {
+									Kind: &structpb.Value_StringValue{StringValue: "fake-url"},
+								},
+							},
+						}}, nil
+					},
+					Delete: func(ctx context.Context, in *pulumirpc.DeleteRequest) (*emptypb.Empty, error) {
+						return &emptypb.Empty{}, nil
+					},
+				})))
+		test.Preview()
+		test.Up()
+		assert.True(t, attached, "expected Attach to be called in mock")
+		assert.True(t, configured, "expected Configure to be called in mock")
+		assert.True(t, checkedConfig, "expected CheckConfig to be called in mock")
+		assert.True(t, checked, "expected Check to be called in mock")
+		assert.True(t, created, "expected Create to be called in mock")
+	})
+}
diff --git a/pulumitest/testdata/python_gcp/.gitignore b/pulumitest/testdata/python_gcp/.gitignore
new file mode 100644
index 0000000..b664ab4
--- /dev/null
+++ b/pulumitest/testdata/python_gcp/.gitignore
@@ -0,0 +1,2 @@
+*.pyc
+venv/
\ No newline at end of file
diff --git a/pulumitest/testdata/python_gcp/Pulumi.yaml b/pulumitest/testdata/python_gcp/Pulumi.yaml
new file mode 100644
index 0000000..e59269c
--- /dev/null
+++ b/pulumitest/testdata/python_gcp/Pulumi.yaml
@@ -0,0 +1,3 @@
+name: yaml_gcp
+runtime: python
+description: A minimal Google Cloud Pulumi YAML program
diff --git a/pulumitest/testdata/python_gcp/__main__.py b/pulumitest/testdata/python_gcp/__main__.py
new file mode 100644
index 0000000..2522f51
--- /dev/null
+++ b/pulumitest/testdata/python_gcp/__main__.py
@@ -0,0 +1,6 @@
+import pulumi
+import pulumi_gcp as gcp
+
+provider = gcp.Provider("provider")
+my_bucket = gcp.storage.Bucket("my-bucket", location="US")
+pulumi.export("bucketName", my_bucket.url)
diff --git a/pulumitest/testdata/python_gcp/requirements.txt b/pulumitest/testdata/python_gcp/requirements.txt
new file mode 100644
index 0000000..7c64591
--- /dev/null
+++ b/pulumitest/testdata/python_gcp/requirements.txt
@@ -0,0 +1,2 @@
+pulumi>=3.0.0,<4.0.0
+pulumi-gcp==7.6.0
diff --git a/replay/replay_test.go b/replay/replay_test.go
index bf138ec..5b9a99b 100644
--- a/replay/replay_test.go
+++ b/replay/replay_test.go
@@ -22,7 +22,7 @@ func TestReplayNormalizesCheckFailureOrder(t *testing.T) {
 		{Property: "A", Reason: "A-failed"},
 	}
 
-	p, err := providers.NewProviderMock(context.Background(), providers.ProviderMocks{
+	p, err := providers.NewProviderMock(providers.ProviderMocks{
 		CheckConfig: func(ctx context.Context, in *pulumirpc.CheckRequest) (*pulumirpc.CheckResponse, error) {
 			return &pulumirpc.CheckResponse{Failures: failures}, nil
 		},
@@ -124,7 +124,7 @@ func TestReplayNormalizesCheckFailureOrder(t *testing.T) {
 }
 
 func TestMatchingErrors(t *testing.T) {
-	p, err := providers.NewProviderMock(context.Background(), providers.ProviderMocks{
+	p, err := providers.NewProviderMock(providers.ProviderMocks{
 		Check: func(ctx context.Context, in *pulumirpc.CheckRequest) (*pulumirpc.CheckResponse, error) {
 			return &pulumirpc.CheckResponse{}, fmt.Errorf("An error has occurred")
 		},