add testcase for in-memory merklytree

Author: junyu0312

test/db.test.ts

@@ -3,7 +3,7 @@ import { MarkleTree } from "../src/markle-tree-large";
 
 var assert = require('assert');
 
-async function main() {
+async function testDBMerkleTree() {
     const merkle_tree = new MarkleTree();
 
     await merkle_tree.loadSnapshot("0");
@@ -55,4 +55,32 @@ async function main() {
     await merkle_tree.closeDb();
 }
 
+async function testInMemoryMerkleTree() {
+    const merkle_tree = new MarkleTree(true);
+
+    await merkle_tree.getNode("0001").then((node) => {
+        assert.ok(node === undefined)
+    });
+
+    await merkle_tree.setNode("0001", new Field(1));
+    await merkle_tree.getNode("0001").then((node) => {
+        assert.ok(node!.v.eq(new Field(1).v))
+    });
+
+    // lastestSnapshot should always return string "0"
+    await merkle_tree.lastestSnapshot().then((node) => {
+        assert.equal(node, "0");
+    });
+
+    // should do nothing
+    await merkle_tree.loadSnapshot("0");
+    await merkle_tree.endSnapshot();
+    await merkle_tree.closeDb();
+}
+
+async function main() {
+    await testDBMerkleTree();
+    await testInMemoryMerkleTree();
+}
+
 main().then(() => console.log("done"))