test: add mock spanner test

Author: alkatrivedi

system-test/spanner.ts

@@ -9214,13 +9214,11 @@ describe('Spanner', () => {
 
             // increament the shared counter
             sync.count++;
-            if (sync.count === sync.target) {
-              sync.openPromise();
-            }
 
-            // both the transactions will pause till count equals target
-            // (or wait for the both the transaction to ready for commit)
-            await sync.promise;
+            while (sync.count !== sync.target) {
+              // wait for 500 milliseconds
+              await new Promise(resolve => setTimeout(resolve, 500));
+            }
 
             // commit the transaction once both the transactions are ready to commit
             await transaction!.commit();
@@ -9229,15 +9227,9 @@ describe('Spanner', () => {
 
         it('GOOGLE_STANDARD_SQL should insert and commit transaction when running parallely', async () => {
           const promises: Promise<void>[] = [];
-          let resolvePromise;
-          const commitPromise = new Promise(
-            resolve => (resolvePromise = resolve),
-          );
           const sync = {
             target: 2, // both the transactions to be ready
-            count: 0, // 0 transactions are so far
-            promise: commitPromise, // the promise both the transactions wait at
-            openPromise: () => resolvePromise(),
+            count: 0, // 0 transactions are ready so far
           };
           // run the transactions in parallel
           promises.push(
@@ -9253,15 +9245,9 @@ describe('Spanner', () => {
 
         it('POSTGRESQL should insert and commit transactions when running parallely', async () => {
           const promises: Promise<void>[] = [];
-          let resolvePromise;
-          const commitPromise = new Promise(
-            resolve => (resolvePromise = resolve),
-          );
           const sync = {
             target: 2, // both the transactions to be ready
-            count: 0, // 0 transactions are so far
-            promise: commitPromise, // the promise both the transactions wait at
-            openPromise: () => resolvePromise(),
+            count: 0, // 0 transactions are ready so far
           };
           // run the transactions in parallel
           promises.push(

test/spanner.ts

@@ -4734,6 +4734,65 @@ describe('Spanner with mock server', () => {
           await database.close();
         });
       });
+
+      // parallel transactions
+      describe('parallel transactions', async () => {
+        async function insertAndCommit() {
+          const database = newTestDatabase();
+          await database.runTransactionAsync(async tx => {
+            tx.upsert('foo', [
+              {id: 1, name: 'One'},
+              {id: 2, name: 'Two'},
+            ]);
+            await tx.commit();
+          });
+        }
+        it('should have different precommit tokens for each transactions when running parallely', async () => {
+          const promises: Promise<void>[] = [];
+
+          // run the transactions parallely
+          promises.push(insertAndCommit());
+          promises.push(insertAndCommit());
+
+          // wait for the transaction to complete its execution
+          await Promise.all(promises);
+
+          const commitRequest = spannerMock.getRequests().filter(val => {
+            return (val as v1.CommitRequest).precommitToken;
+          }) as v1.CommitRequest[];
+
+          // assert that there are two commit requests one for each transaction
+          assert.strictEqual(commitRequest.length, 2);
+
+          // assert that precommitToken is not null during first request to commit
+          assert.notEqual(commitRequest[0].precommitToken, null);
+
+          // assert that precommitToken is instance of Buffer
+          assert.ok(
+            commitRequest[0].precommitToken?.precommitToken instanceof Buffer,
+          );
+
+          // assert that precommitToken is not null during second request to commit
+          assert.notEqual(commitRequest[1].precommitToken, null);
+
+          // assert that precommitToken is instance of Buffer
+          assert.ok(
+            commitRequest[1].precommitToken?.precommitToken instanceof Buffer,
+          );
+
+          // assert that precommitToken is different in both the commit request
+          assert.notEqual(
+            commitRequest[0].precommitToken.precommitToken,
+            commitRequest[1].precommitToken.precommitToken,
+          );
+
+          // assert that seqNum is different in both the commit request
+          assert.notEqual(
+            commitRequest[0].precommitToken.seqNum,
+            commitRequest[1].precommitToken.seqNum,
+          );
+        });
+      });
     });
   });