diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
new file mode 100644
index 0000000..26f0f3b
--- /dev/null
+++ b/.github/workflows/build.yml
@@ -0,0 +1,53 @@
+name: Build
+
+on:
+  push:
+    branches:
+      - develop
+  pull_request:
+
+jobs:
+
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up Node
+      uses: actions/setup-node@v4
+      with:
+        node-version: 20
+        cache: 'npm'
+        cache-dependency-path: package-lock.json
+    - name: Install dependencies
+      run: npm install
+
+    - name: Build docs
+      run: npm run build:docs
+    - name: Fail if documentation.md changed
+      run: |
+        if git diff --exit-code ./docs/documentation.md; then
+          echo "documentation.md unchanged."
+        else
+          echo "::error file=docs/documentation.md::documentation.md is out of date. Please rebuild docs and commit the changes."
+          exit 1
+        fi
+
+    - name: Build types
+      run: npm run build:types
+    - name: Fail if index.d.ts changed
+      run: |
+        if git diff --exit-code ./lib/types/host/index.d.ts; then
+          echo "index.d.ts unchanged."
+        else
+          echo "::error file=lib/types/host/index.d.ts::index.d.ts is out of date. Please rebuild types and commit the changes."
+          exit 1
+        fi
+
+    - name: Test lib
+      run: npm run test:dev
+
+    - name: Build example
+      run: npm run build
+
+    - name: Test example
+      run: npm run test
diff --git a/devtests/json.test.js b/devtests/json.test.js
new file mode 100644
index 0000000..76ff137
--- /dev/null
+++ b/devtests/json.test.js
@@ -0,0 +1,38 @@
+import { describe, it, afterEach } from 'node:test';
+import assert from 'assert';
+import { buildScript, resolvePath } from './testutils.js';
+
+const script = await buildScript(resolvePath(import.meta.url, 'json.test.ts'));
+
+await describe('JSON', async () => {
+
+	afterEach(() => {
+		// Garbage collect after each test.
+		script.__collect();
+	});
+
+	it('jsonParseEventChar parses an Event.Char json structure', () => {
+		assert.doesNotThrow(() => script.jsonParseEventChar());
+	});
+
+	it('jsonParseEventBase parses an Event.Base json structure', () => {
+		assert.doesNotThrow(() => script.jsonParseEventBase());
+	});
+
+	it('jsonParseEventBaseCharMsg parses an Event.BaseCharMsg json structure', () => {
+		assert.doesNotThrow(() => script.jsonParseEventBaseCharMsg());
+	});
+
+	it('jsonParseEventBaseCharMsgCharBeforeMsg parses an Event.BaseCharMsg json structure with char appearing before msg', () => {
+		assert.doesNotThrow(() => script.jsonParseEventBaseCharMsgCharBeforeMsg());
+	});
+
+	it('eventGetTypeBaseCharMsg calls Event.getType on a Event.BaseCharMsg json structure', () => {
+		assert.doesNotThrow(() => script.eventGetTypeBaseCharMsg());
+	});
+
+	it('jsonParseEventSay parses an Event.Say json structure', () => {
+		assert.doesNotThrow(() => script.jsonParseEventSay());
+	});
+
+});
diff --git a/devtests/json.test.ts b/devtests/json.test.ts
new file mode 100644
index 0000000..4583936
--- /dev/null
+++ b/devtests/json.test.ts
@@ -0,0 +1,59 @@
+// Event.Char
+const charId = "aaaabbbbccccddddeeee"
+const charName = "Jane"
+const charSurname = "Doe"
+const eventCharDta = `{"id":"${charId}","name":"${charName}","surname":"${charSurname}"}`
+function assertEventChar(char: Event.Char): void {
+	assert(char.id == charId, `expected char.id to be "${charId}", but got "${char.id}".`)
+	assert(char.name == charName, `expected char.name to be "${charName}", but got "${char.name}".`)
+	assert(char.surname == charSurname, `expected char.surname to be "${charSurname}", but got "${char.surname}".`)
+}
+
+// Event.Base
+const baseId = "aaaaaaaaaaaaaaaaaaaa"
+const baseType = "foo"
+const baseTime = 1136210645000
+const baseSig = "SIGNATUREAAABBBCCC"
+const eventBaseDta = `{"id":"${baseId}","type":"${baseType}","time":${baseTime.toString()},"sig":"${baseSig}"}`
+function assertEventBase(base: Event.Base): void  {
+	assert(base.id == baseId, `expected base.id to be "${baseId}", but got "${base.id}".`)
+	assert(base.type == baseType, `expected base.type to be "${baseType}", but got "${base.type}".`)
+	assert(base.time == baseTime, `expected base.time to be ${baseTime.toString()}, but got ${base.time.toString()}.`)
+	assert(base.sig == baseSig, `expected base.sig to be "${baseSig}", but got "${base.sig}".`)
+}
+
+// Event.BaseCharMsg
+const baseMsg = "Lorem ipsum"
+const eventBaseCharMsgDta = `{"id":"${baseId}","type":"${baseType}","time":${baseTime.toString()},"sig":"${baseSig}","msg":"${baseMsg}","char":${eventCharDta}}`
+const eventBaseCharMsgDtaCharBeforeMsg = `{"char":${eventCharDta},"id":"${baseId}","type":"${baseType}","time":${baseTime.toString()},"sig":"${baseSig}","msg":"${baseMsg}"}`
+function assertEventBaseCharMsg(baseCharMsg: Event.BaseCharMsg): void  {
+	assertEventBase(baseCharMsg as Event.Base)
+	assertEventChar(baseCharMsg.char)
+	assert(baseCharMsg.msg == baseMsg, `expected baseCharMsg.msg to be "${baseMsg}", but got "${baseCharMsg.msg}".`)
+}
+
+
+export function jsonParseEventChar(): void {
+	// assertEventChar(JSON.parse<Event.Char>(eventCharDta))
+}
+
+export function jsonParseEventBase(): void {
+	assertEventBase(JSON.parse<Event.Base>(eventBaseDta))
+}
+
+export function jsonParseEventBaseCharMsg(): void {
+	// assertEventBaseCharMsg(JSON.parse<Event.BaseCharMsg>(eventBaseCharMsgDta))
+}
+
+export function jsonParseEventBaseCharMsgCharBeforeMsg(): void {
+	// assertEventBaseCharMsg(JSON.parse<Event.BaseCharMsg>(eventBaseCharMsgDtaCharBeforeMsg))
+}
+
+export function eventGetTypeBaseCharMsg(): void {
+	// const t = Event.getType(eventBaseCharMsgDta)
+	// assert(t == baseType, `expected base.type to be "${baseType}", but got "${t}".`)
+}
+
+export function jsonParseEventSay(): void {
+	// assertEventBaseCharMsg(JSON.parse<Event.Say>(eventBaseCharMsgDtaCharBeforeMsg))
+}
diff --git a/devtests/room.test.js b/devtests/room.test.js
new file mode 100644
index 0000000..e96b07a
--- /dev/null
+++ b/devtests/room.test.js
@@ -0,0 +1,112 @@
+import { describe, it, beforeEach, afterEach, mock } from 'node:test';
+import assert from 'assert';
+import { buildScript, resolvePath, mockGlobal } from './testutils.js';
+
+const script = await buildScript(resolvePath(import.meta.url, 'room.test.ts'));
+
+await describe('Room', async () => {
+
+	beforeEach(() => {
+		mockGlobal(global);
+	});
+
+	afterEach(() => {
+		// Garbage collect after each test.
+		script.__collect();
+	});
+
+	it('abortWithString aborts and throws error', () => {
+		assert.throws(() => script.abortWithString());
+	});
+
+	it('roomDescribe calls room.describe', () => {
+		assert.doesNotThrow(() => script.roomDescribe());
+		assert.strictEqual(global.room.describe.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.describe.mock.calls[0].arguments, [ "foo" ]);
+	});
+
+	it('roomListen without arguments calls room.listen', () => {
+		global.room.listen = mock.fn((instance) => true);
+		assert.doesNotThrow(() => script.roomListen(true, null));
+		assert.strictEqual(global.room.listen.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.listen.mock.calls[0].arguments, [ 0, null ]);
+	});
+
+	it('roomListen with instance calls room.listen', () => {
+		global.room.listen = mock.fn((instance) => false);
+		assert.doesNotThrow(() => script.roomListen(false, "instance"));
+		assert.strictEqual(global.room.listen.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.listen.mock.calls[0].arguments, [ 0, 'instance' ]);
+	});
+
+	it('roomUnlisten without arguments calls room.unlisten', () => {
+		global.room.unlisten = mock.fn((instance) => true);
+		assert.doesNotThrow(() => script.roomUnlisten(true, null));
+		assert.strictEqual(global.room.unlisten.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.unlisten.mock.calls[0].arguments, [ 0, null ]);
+	});
+
+	it('roomUnlisten with instance calls room.unlisten', () => {
+		global.room.unlisten = mock.fn((instance) => false);
+		assert.doesNotThrow(() => script.roomUnlisten(false, "instance"));
+		assert.strictEqual(global.room.unlisten.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.unlisten.mock.calls[0].arguments, [ 0, 'instance' ]);
+	});
+
+	it('roomListenCharEvent without arguments calls room.listen', () => {
+		global.room.listen = mock.fn((instance) => true);
+		assert.doesNotThrow(() => script.roomListenCharEvent(true, null));
+		assert.strictEqual(global.room.listen.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.listen.mock.calls[0].arguments, [ 1, null ]);
+	});
+
+	it('roomListenCharEvent with instance calls room.listen', () => {
+		global.room.listen = mock.fn((instance) => false);
+		assert.doesNotThrow(() => script.roomListenCharEvent(false, "instance"));
+		assert.strictEqual(global.room.listen.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.listen.mock.calls[0].arguments, [ 1, 'instance' ]);
+	});
+
+	it('roomUnlistenCharEvent without arguments calls room.unlisten', () => {
+		global.room.unlisten = mock.fn((instance) => true);
+		assert.doesNotThrow(() => script.roomUnlistenCharEvent(true, null));
+		assert.strictEqual(global.room.unlisten.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.unlisten.mock.calls[0].arguments, [ 1, null ]);
+	});
+
+	it('roomUnlistenCharEvent with instance calls room.unlisten', () => {
+		global.room.unlisten = mock.fn((instance) => false);
+		assert.doesNotThrow(() => script.roomUnlistenCharEvent(false, "instance"));
+		assert.strictEqual(global.room.unlisten.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.unlisten.mock.calls[0].arguments, [ 1, 'instance' ]);
+	});
+
+	it('roomListenExit without arguments calls room.listenExit', () => {
+		global.room.listenExit = mock.fn((instance) => true);
+		assert.doesNotThrow(() => script.roomListenExit(true, null));
+		assert.strictEqual(global.room.listenExit.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.listenExit.mock.calls[0].arguments, [ null ]);
+	});
+
+	it('roomListenExit with instance calls room.listenExit', () => {
+		global.room.listenExit = mock.fn((instance) => false);
+		assert.doesNotThrow(() => script.roomListenExit(false, "exitId"));
+		assert.strictEqual(global.room.listenExit.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.listenExit.mock.calls[0].arguments, [ 'exitId' ]);
+	});
+
+	it('roomUnlistenExit without arguments calls room.unlistenExit', () => {
+		global.room.unlistenExit = mock.fn((instance) => true);
+		assert.doesNotThrow(() => script.roomUnlistenExit(true, null));
+		assert.strictEqual(global.room.unlistenExit.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.unlistenExit.mock.calls[0].arguments, [ null ]);
+	});
+
+	it('roomUnlistenExit with instance calls room.unlistenExit', () => {
+		global.room.unlistenExit = mock.fn((instance) => false);
+		assert.doesNotThrow(() => script.roomUnlistenExit(false, "exitid"));
+		assert.strictEqual(global.room.unlistenExit.mock.callCount(), 1);
+		assert.deepStrictEqual(global.room.unlistenExit.mock.calls[0].arguments, [ 'exitid' ]);
+	});
+
+});
diff --git a/devtests/room.test.ts b/devtests/room.test.ts
new file mode 100644
index 0000000..5602b82
--- /dev/null
+++ b/devtests/room.test.ts
@@ -0,0 +1,37 @@
+export function abortWithString(): void {
+	abort("foo error", "room.test.js", 2, 1)
+}
+
+export function roomDescribe(): void {
+	Room.describe("foo")
+}
+
+export function roomListen(expected: boolean, instance: string | null = null): void {
+	const returnValue = Room.listen(instance)
+	assert(returnValue == expected, `expected return value to be ${expected.toString()}, but got ${returnValue.toString()}.`)
+}
+
+export function roomUnlisten(expected: boolean, instance: string | null = null): void {
+	const returnValue = Room.unlisten(instance)
+	assert(returnValue == expected, `expected return value to be ${expected.toString()}, but got ${returnValue.toString()}.`)
+}
+
+export function roomListenCharEvent(expected: boolean, instance: string | null = null): void {
+	const returnValue = Room.listenCharEvent(instance)
+	assert(returnValue == expected, `expected return value to be ${expected.toString()}, but got ${returnValue.toString()}.`)
+}
+
+export function roomUnlistenCharEvent(expected: boolean, instance: string | null = null): void {
+	const returnValue = Room.unlistenCharEvent(instance)
+	assert(returnValue == expected, `expected return value to be ${expected.toString()}, but got ${returnValue.toString()}.`)
+}
+
+export function roomListenExit(expected: boolean, exitId: string | null = null): void {
+	const returnValue = Room.listenExit(exitId)
+	assert(returnValue == expected, `expected return value to be ${expected.toString()}, but got ${returnValue.toString()}.`)
+}
+
+export function roomUnlistenExit(expected: boolean, exitId: string | null = null): void {
+	const returnValue = Room.unlistenExit(exitId)
+	assert(returnValue == expected, `expected return value to be ${expected.toString()}, but got ${returnValue.toString()}.`)
+}
diff --git a/devtests/testutils.js b/devtests/testutils.js
new file mode 100644
index 0000000..9c21dce
--- /dev/null
+++ b/devtests/testutils.js
@@ -0,0 +1,66 @@
+
+import path from 'path';
+import { mock } from 'node:test';
+import { rootDir, compileScript } from '../bin/utils/tools.js';
+import { fileURLToPath, pathToFileURL} from "url";
+
+const buildDir = path.join(rootDir, 'build');
+
+/**
+ * Resolves a full path from a import.meta.url to a file in posix format.
+ * @param {string} url Import meta url to resolve from
+ * @param {string} filePath File path (with posix separators is used)
+ */
+export function resolvePath(url, filePath) {
+	return path.join(path.dirname(fileURLToPath(url)), filePath.replaceAll(path.posix.sep, path.sep));
+}
+
+export async function buildScript(scriptPath) {
+	const filename = path.parse(scriptPath).name;
+	const outFile = path.join(buildDir, filename + '.wasm');
+	const textFile = path.join(buildDir, filename + '.wat');
+	const scriptFile = path.join(buildDir, filename + '.js');
+
+	try {
+		compileScript(scriptPath, outFile, textFile);
+	} catch (err) {
+		let errMsg = err?.stderr?.toString
+			? err.stderr.toString()
+			: err;
+		throw errMsg;
+	}
+
+	const script = await import(pathToFileURL(scriptFile));
+
+	return script;
+}
+
+export function mockGlobal(global) {
+	global.room = {
+		describe: mock.fn((msg) => {}),
+		listen: mock.fn((instance) => {}),
+		unlisten: mock.fn((instance) => {}),
+		getRoom: mock.fn(() => JSON.stringify(room)),
+		setRoom: mock.fn((json) => {}),
+		useProfile: mock.fn((key, safe) => {}),
+		sweepChar: mock.fn((charId, msg) => {}),
+		canEdit: mock.fn((charId) => true),
+	};
+	global.script = {
+		post: mock.fn((addr, topic, data, delay) => {}),
+		listen: mock.fn((addrs) => {}),
+		unlisten: mock.fn((addrs) => {}),
+	};
+	global.store = {
+		setItem: mock.fn((key, item) => {}),
+		getItem: mock.fn((key) => null),
+		totalBytes: mock.fn(() => 0),
+		newIterator: mock.fn((prefix, reverse) => iterator++),
+		iteratorClose: mock.fn((iterator) => {}),
+		iteratorSeek: mock.fn((iterator, key) => {}),
+		iteratorNext: mock.fn((iterator) => {}),
+		iteratorValid: mock.fn((iterator, prefix) => false),
+		iteratorKey: mock.fn((iterator) => new ArrayBuffer(1)),
+		iteratorItem: mock.fn((iterator) => new ArrayBuffer(1)),
+	};
+}
diff --git a/docs/documentation.md b/docs/documentation.md
index de2795e..7367f2f 100644
--- a/docs/documentation.md
+++ b/docs/documentation.md
@@ -329,6 +329,7 @@ export function onCommand(
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[method from](#method-json-value-from)  
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[method set](#method-json-value-set)  
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[method get](#method-json-value-get)  
+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[method as](#method-json-value-as)  
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[method toString](#method-json-value-tostring)  
 
 <h3 id="namespace-room">Room namespace</h3>
@@ -2326,6 +2327,22 @@ Gets the value of the JSON.Value instance.
 * <i>(T)</i>: The encapsulated value.
 
 
+---
+
+<h3 id="method-json-value-as">method JSON.Value.as</h3>
+
+```ts
+as<T>(): T
+```
+
+Gets the value of the JSON.Value instance.
+Alias for .get<T>()
+
+<h4>Returns</h4>
+
+* <i>(T)</i>: The encapsulated value.
+
+
 ---
 
 <h3 id="method-json-value-tostring">method JSON.Value.toString</h3>
diff --git a/package-lock.json b/package-lock.json
index b485b9f..335ba88 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -11,7 +11,7 @@
       "dependencies": {
         "assemblyscript": "^0.28.2",
         "isomorphic-ws": "^5.0.0",
-        "json-as": "1.1.9",
+        "json-as": "github:anisus/json-as",
         "resclient": "^2.5.0",
         "tinyargs": "^0.1.4",
         "visitor-as": "^0.11.4"
@@ -502,9 +502,9 @@
       "dev": true
     },
     "node_modules/brace-expansion": {
-      "version": "1.1.11",
-      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-1.1.11.tgz",
-      "integrity": "sha512-iCuPHDFgrHX7H2vEI/5xpz07zSHB00TpugqhmYtVmMO6518mCuRMoOYFldEBl0g187ufozdaHgWKcYFb61qGiA==",
+      "version": "1.1.12",
+      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-1.1.12.tgz",
+      "integrity": "sha512-9T9UjW3r0UW5c1Q7GTwllptXwhvYmEzFhzMfZ9H7FQWt+uZePjZPjBP/W1ZEyZ1twGWom5/56TF4lPcqjnDHcg==",
       "dev": true,
       "dependencies": {
         "balanced-match": "^1.0.0",
@@ -1085,9 +1085,8 @@
       }
     },
     "node_modules/json-as": {
-      "version": "1.1.9",
-      "resolved": "https://registry.npmjs.org/json-as/-/json-as-1.1.9.tgz",
-      "integrity": "sha512-ts7mro8xtgZz7eiuxSLrqVqwXBrWm2J0vHgqVFD1RR2QNfNGQKjiXHXvaGzp1uLY4Vf+76yHfq8mEyxx+02ZKw=="
+      "version": "1.1.16",
+      "resolved": "git+ssh://git@github.com/anisus/json-as.git#f9e640b23b1e3c311dbb7ca2d48219ed9e779717"
     },
     "node_modules/json-buffer": {
       "version": "3.0.1",
@@ -1581,9 +1580,9 @@
       }
     },
     "node_modules/typedoc/node_modules/brace-expansion": {
-      "version": "2.0.1",
-      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-2.0.1.tgz",
-      "integrity": "sha512-XnAIvQ8eM+kC6aULx6wuQiwVsnzsi9d3WxzV3FpWTGA19F621kwdbsAcFKXgKUHZWsy+mY6iL1sHTxWEFCytDA==",
+      "version": "2.0.2",
+      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-2.0.2.tgz",
+      "integrity": "sha512-Jt0vHyM+jmUBqojB7E1NIYadt0vI0Qxjxd2TErW94wDz+E2LAm5vKMXXwg6ZZBTHPuUlDgQHKXvjGBdfcF1ZDQ==",
       "dev": true,
       "dependencies": {
         "balanced-match": "^1.0.0"
diff --git a/package.json b/package.json
index baf16f6..71da145 100644
--- a/package.json
+++ b/package.json
@@ -3,6 +3,7 @@
   "version": "1.66.1",
   "scripts": {
     "test": "node tests",
+    "test:dev": "node --test",
     "build": "asc scripts/index.ts --runtime minimal --exportRuntime --lib ./lib/host.ts --lib ./lib/env.ts",
     "build:types": "node devbin/buildtypes.js",
     "build:docs": "node devbin/builddocs.js"
@@ -36,7 +37,7 @@
   "dependencies": {
     "assemblyscript": "^0.28.2",
     "isomorphic-ws": "^5.0.0",
-    "json-as": "1.1.9",
+    "json-as": "github:anisus/json-as",
     "resclient": "^2.5.0",
     "tinyargs": "^0.1.4",
     "visitor-as": "^0.11.4"