diff --git a/spanner/spannertest/README.md b/spanner/spannertest/README.md
index 6f820f97e52..d05f9d277c6 100644
--- a/spanner/spannertest/README.md
+++ b/spanner/spannertest/README.md
@@ -19,16 +19,16 @@ by ascending esotericism:
 
 - expression functions
 - more aggregation functions
-- INSERT/UPDATE DML statements
 - SELECT HAVING
 - case insensitivity
-- FULL JOIN
+- FULL JOIN, multiple joins
 - alternate literal types (esp. strings)
 - STRUCT types
 - transaction simulation
 - expression type casting, coercion
 - subselects
 - FOREIGN KEY and CHECK constraints
+- INSERT DML statements
 - set operations (UNION, INTERSECT, EXCEPT)
 - partition support
 - conditional expressions
diff --git a/spanner/spannertest/db.go b/spanner/spannertest/db.go
index 810bcecae27..d1a9ef20df0 100644
--- a/spanner/spannertest/db.go
+++ b/spanner/spannertest/db.go
@@ -999,6 +999,65 @@ func (d *database) Execute(stmt spansql.DMLStmt, params queryParams) (int, error
 			i++
 		}
 		return n, nil
+	case *spansql.Update:
+		t, err := d.table(stmt.Table)
+		if err != nil {
+			return 0, err
+		}
+
+		t.mu.Lock()
+		defer t.mu.Unlock()
+
+		ec := evalContext{
+			cols:   t.cols,
+			params: params,
+		}
+
+		// Build parallel slices of destination column index and expressions to evaluate.
+		var dstIndex []int
+		var expr []spansql.Expr
+		for _, ui := range stmt.Items {
+			i, err := ec.resolveColumnIndex(ui.Column)
+			if err != nil {
+				return 0, err
+			}
+			// TODO: Enforce "A column can appear only once in the SET clause.".
+			if i < t.pkCols {
+				return 0, status.Errorf(codes.InvalidArgument, "cannot update primary key %s", ui.Column)
+			}
+			dstIndex = append(dstIndex, i)
+			expr = append(expr, ui.Value)
+		}
+
+		n := 0
+		values := make(row, len(stmt.Items)) // scratch space for new values
+		for i := 0; i < len(t.rows); i++ {
+			ec.row = t.rows[i]
+			b, err := ec.evalBoolExpr(stmt.Where)
+			if err != nil {
+				return 0, err
+			}
+			if b != nil && *b {
+				// Compute every update item.
+				for j := range dstIndex {
+					if expr[j] == nil { // DEFAULT
+						values[j] = nil
+						continue
+					}
+					v, err := ec.evalExpr(expr[j])
+					if err != nil {
+						return 0, err
+					}
+					values[j] = v
+				}
+				// Write them to the row.
+				for j, v := range values {
+					t.rows[i][dstIndex[j]] = v
+				}
+				n++
+			}
+		}
+		return n, nil
 	}
 }
 
diff --git a/spanner/spannertest/integration_test.go b/spanner/spannertest/integration_test.go
index adbe329808e..f70b01f84b8 100644
--- a/spanner/spannertest/integration_test.go
+++ b/spanner/spannertest/integration_test.go
@@ -412,7 +412,7 @@ func TestIntegration_ReadsAndQueries(t *testing.T) {
 		"Staff",
 		"PlayerStats",
 		"JoinA", "JoinB", "JoinC", "JoinD", "JoinE", "JoinF",
-		"SomeStrings",
+		"SomeStrings", "Updateable",
 	}
 	errc := make(chan error)
 	for _, table := range allTables {
@@ -618,6 +618,11 @@ func TestIntegration_ReadsAndQueries(t *testing.T) {
 		`CREATE TABLE JoinF ( y INT64, z STRING(MAX) ) PRIMARY KEY (y, z)`,
 		// Some other test tables.
 		`CREATE TABLE SomeStrings ( i INT64, str STRING(MAX) ) PRIMARY KEY (i)`,
+		`CREATE TABLE Updateable (
+			id INT64,
+			first STRING(MAX),
+			last STRING(MAX),
+		) PRIMARY KEY (id)`,
 	)
 	if err != nil {
 		t.Fatalf("Creating sample tables: %v", err)
@@ -661,11 +666,39 @@ func TestIntegration_ReadsAndQueries(t *testing.T) {
 		spanner.Insert("SomeStrings", []string{"i", "str"}, []interface{}{1, "abar"}),
 		spanner.Insert("SomeStrings", []string{"i", "str"}, []interface{}{2, nil}),
 		spanner.Insert("SomeStrings", []string{"i", "str"}, []interface{}{3, "bbar"}),
+
+		spanner.Insert("Updateable", []string{"id", "first", "last"}, []interface{}{0, "joe", nil}),
+		spanner.Insert("Updateable", []string{"id", "first", "last"}, []interface{}{1, "doe", "joan"}),
+		spanner.Insert("Updateable", []string{"id", "first", "last"}, []interface{}{2, "wong", "wong"}),
 	})
 	if err != nil {
 		t.Fatalf("Inserting sample data: %v", err)
 	}
 
+	// Perform UPDATE DML; the results are checked later on.
+	n = 0
+	_, err = client.ReadWriteTransaction(ctx, func(ctx context.Context, tx *spanner.ReadWriteTransaction) error {
+		for _, u := range []string{
+			`UPDATE Updateable SET last = "bloggs" WHERE id = 0`,
+			`UPDATE Updateable SET first = last, last = first WHERE id = 1`,
+			`UPDATE Updateable SET last = DEFAULT WHERE id = 2`,
+			`UPDATE Updateable SET first = "noname" WHERE id = 3`, // no id=3
+		} {
+			nr, err := tx.Update(ctx, spanner.NewStatement(u))
+			if err != nil {
+				return err
+			}
+			n += nr
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatalf("Updating with DML: %v", err)
+	}
+	if n != 3 {
+		t.Errorf("Updating with DML affected %d rows, want 3", n)
+	}
+
 	// Do some complex queries.
 	tests := []struct {
 		q      string
@@ -976,6 +1009,16 @@ func TestIntegration_ReadsAndQueries(t *testing.T) {
 				{int64(4), nil, "p"},
 			},
 		},
+		// Check the output of the UPDATE DML.
+		{
+			`SELECT id, first, last FROM Updateable ORDER BY id`,
+			nil,
+			[][]interface{}{
+				{int64(0), "joe", "bloggs"},
+				{int64(1), "joan", "doe"},
+				{int64(2), "wong", nil},
+			},
+		},
 		// Regression test for aggregating no rows; it used to return an empty row.
 		// https://github.com/googleapis/google-cloud-go/issues/2793
 		{