diff --git a/backend/local/backend_apply_test.go b/backend/local/backend_apply_test.go
index e7e7a53a9..f8de90479 100644
--- a/backend/local/backend_apply_test.go
+++ b/backend/local/backend_apply_test.go
@@ -123,8 +123,7 @@ func TestLocal_applyError(t *testing.T) {
 	b, cleanup := TestLocal(t)
 	defer cleanup()
 
-	p := TestLocalProvider(t, b, "test", nil)
-	p.GetSchemaReturn = &terraform.ProviderSchema{
+	schema := &terraform.ProviderSchema{
 		ResourceTypes: map[string]*configschema.Block{
 			"test_instance": {
 				Attributes: map[string]*configschema.Attribute{
@@ -134,6 +133,7 @@ func TestLocal_applyError(t *testing.T) {
 			},
 		},
 	}
+	p := TestLocalProvider(t, b, "test", schema)
 
 	var lock sync.Mutex
 	errored := false
diff --git a/backend/local/testing.go b/backend/local/testing.go
index 05f7600f9..dccddb5da 100644
--- a/backend/local/testing.go
+++ b/backend/local/testing.go
@@ -6,7 +6,11 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/zclconf/go-cty/cty"
+
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/backend"
+	"github.com/hashicorp/terraform/configs/configschema"
 	"github.com/hashicorp/terraform/providers"
 	"github.com/hashicorp/terraform/states"
 	"github.com/hashicorp/terraform/states/statemgr"
@@ -38,9 +42,14 @@ func TestLocal(t *testing.T) (*Local, func()) {
 			// function, t.Helper doesn't apply and so the log source
 			// isn't correctly shown in the test log output. This seems
 			// unavoidable as long as this is happening so indirectly.
-			t.Log(diag.Description().Summary)
+			desc := diag.Description()
+			if desc.Detail != "" {
+				t.Logf("%s: %s", desc.Summary, desc.Detail)
+			} else {
+				t.Log(desc.Summary)
+			}
 			if local.CLI != nil {
-				local.CLI.Error(diag.Description().Summary)
+				local.CLI.Error(desc.Summary)
 			}
 		}
 	}
@@ -59,10 +68,34 @@ func TestLocal(t *testing.T) (*Local, func()) {
 func TestLocalProvider(t *testing.T, b *Local, name string, schema *terraform.ProviderSchema) *terraform.MockProvider {
 	// Build a mock resource provider for in-memory operations
 	p := new(terraform.MockProvider)
+
+	if schema == nil {
+		schema = &terraform.ProviderSchema{} // default schema is empty
+	}
 	p.GetSchemaReturn = schema
+
 	p.PlanResourceChangeFn = func(req providers.PlanResourceChangeRequest) providers.PlanResourceChangeResponse {
+		rSchema, _ := schema.SchemaForResourceType(addrs.ManagedResourceMode, req.TypeName)
+		if rSchema == nil {
+			rSchema = &configschema.Block{} // default schema is empty
+		}
+		plannedVals := map[string]cty.Value{}
+		for name, attrS := range rSchema.Attributes {
+			val := req.ProposedNewState.GetAttr(name)
+			if attrS.Computed && val.IsNull() {
+				val = cty.UnknownVal(attrS.Type)
+			}
+			plannedVals[name] = val
+		}
+		for name := range rSchema.BlockTypes {
+			// For simplicity's sake we just copy the block attributes over
+			// verbatim, since this package's mock providers are all relatively
+			// simple -- we're testing the backend, not esoteric provider features.
+			plannedVals[name] = req.ProposedNewState.GetAttr(name)
+		}
+
 		return providers.PlanResourceChangeResponse{
-			PlannedState:   req.ProposedNewState,
+			PlannedState:   cty.ObjectVal(plannedVals),
 			PlannedPrivate: req.PriorPrivate,
 		}
 	}