diff --git a/test/editor/model-test.js b/test/editor/model-test.js
new file mode 100644
index 0000000000..cd435a79a9
--- /dev/null
+++ b/test/editor/model-test.js
@@ -0,0 +1,193 @@
+/*
+Copyright 2019 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import expect from 'expect';
+import EditorModel from "../../src/editor/model";
+import {PartCreator} from "../../src/editor/parts";
+
+class MockAutoComplete {
+    constructor(updateCallback, partCreator, completions) {
+        this._updateCallback = updateCallback;
+        this._partCreator = partCreator;
+        this._completions = completions;
+        this._part = null;
+    }
+
+    close() {
+        this._updateCallback({close: true});
+    }
+
+    tryComplete(close = true) {
+        const matches = this._completions.filter(o => {
+            return o.resourceId.startsWith(this._part.text);
+        });
+        if (matches.length === 1 && this._part.text.length > 1) {
+            const match = matches[0];
+            let pill;
+            if (match.resourceId[0] === "@") {
+                pill = this._partCreator.userPill(match.label, match.resourceId);
+            } else {
+                pill = this._partCreator.roomPill(match.resourceId);
+            }
+            this._updateCallback({replacePart: pill, close});
+        }
+    }
+
+    // called by EditorModel when typing into pill-candidate part
+    onPartUpdate(part, offset) {
+        this._part = part;
+    }
+}
+
+// MockClient & MockRoom are only used for avatars in room and user pills,
+// which is not tested
+class MockClient {
+    getRooms() { return []; }
+    getRoom() { return null; }
+}
+
+class MockRoom {
+    getMember() { return null; }
+}
+
+function createPartCreator(completions = []) {
+    const autoCompleteCreator = (partCreator) => {
+        return (updateCallback) => new MockAutoComplete(updateCallback, partCreator, completions);
+    };
+    return new PartCreator(autoCompleteCreator, new MockRoom(), new MockClient());
+}
+
+function createRenderer() {
+    const render = (c) => {
+        render.caret = c;
+        render.count += 1;
+    };
+    render.count = 0;
+    render.caret = null;
+    return render;
+}
+
+describe('editor/model', function() {
+    describe('plain text manipulation', function() {
+        it('insert text into empty document', function() {
+            const renderer = createRenderer();
+            const model = new EditorModel([], createPartCreator(), renderer);
+            model.update("hello", "insertText", {offset: 5, atNodeEnd: true});
+            expect(renderer.count).toBe(1);
+            expect(renderer.caret.index).toBe(0);
+            expect(renderer.caret.offset).toBe(5);
+            expect(model.parts.length).toBe(1);
+            expect(model.parts[0].type).toBe("plain");
+            expect(model.parts[0].text).toBe("hello");
+        });
+        it('append text to existing document', function() {
+            const renderer = createRenderer();
+            const pc = createPartCreator();
+            const model = new EditorModel([pc.plain("hello")], pc, renderer);
+            model.update("hello world", "insertText", {offset: 11, atNodeEnd: true});
+            expect(renderer.count).toBe(1);
+            expect(renderer.caret.index).toBe(0);
+            expect(renderer.caret.offset).toBe(11);
+            expect(model.parts.length).toBe(1);
+            expect(model.parts[0].type).toBe("plain");
+            expect(model.parts[0].text).toBe("hello world");
+        });
+        it('prepend text to existing document', function() {
+            const renderer = createRenderer();
+            const pc = createPartCreator();
+            const model = new EditorModel([pc.plain("world")], pc, renderer);
+            model.update("hello world", "insertText", {offset: 6, atNodeEnd: false});
+            expect(renderer.count).toBe(1);
+            expect(renderer.caret.index).toBe(0);
+            expect(renderer.caret.offset).toBe(6);
+            expect(model.parts.length).toBe(1);
+            expect(model.parts[0].type).toBe("plain");
+            expect(model.parts[0].text).toBe("hello world");
+        });
+        it('insert new line into existing document', function() {
+            const renderer = createRenderer();
+            const pc = createPartCreator();
+            const model = new EditorModel([pc.plain("hello")], pc, renderer);
+            model.update("hello\n", "insertText", {offset: 6, atNodeEnd: true});
+            expect(renderer.count).toBe(1);
+            expect(renderer.caret.index).toBe(1);
+            expect(renderer.caret.offset).toBe(1);
+            expect(model.parts.length).toBe(2);
+            expect(model.parts[0].type).toBe("plain");
+            expect(model.parts[0].text).toBe("hello");
+            expect(model.parts[1].type).toBe("newline");
+            expect(model.parts[1].text).toBe("\n");
+        });
+    });
+    describe('auto-complete', function() {
+        it('insert user pill', function() {
+            const renderer = createRenderer();
+            const pc = createPartCreator([{resourceId: "@alice", label: "Alice"}]);
+            const model = new EditorModel([pc.plain("hello ")], pc, renderer);
+
+            model.update("hello @a", "insertText", {offset: 8, atNodeEnd: true});
+
+            expect(renderer.count).toBe(1);
+            expect(renderer.caret.index).toBe(1);
+            expect(renderer.caret.offset).toBe(2);
+            expect(model.parts.length).toBe(2);
+            expect(model.parts[0].type).toBe("plain");
+            expect(model.parts[0].text).toBe("hello ");
+            expect(model.parts[1].type).toBe("pill-candidate");
+            expect(model.parts[1].text).toBe("@a");
+
+            model.autoComplete.tryComplete();
+
+            expect(renderer.count).toBe(2);
+            expect(renderer.caret.index).toBe(1);
+            expect(renderer.caret.offset).toBe(5);
+            expect(model.parts.length).toBe(2);
+            expect(model.parts[0].type).toBe("plain");
+            expect(model.parts[0].text).toBe("hello ");
+            expect(model.parts[1].type).toBe("user-pill");
+            expect(model.parts[1].text).toBe("Alice");
+        });
+
+        it('insert room pill', function() {
+            const renderer = createRenderer();
+            const pc = createPartCreator([{resourceId: "#riot-dev"}]);
+            const model = new EditorModel([pc.plain("hello ")], pc, renderer);
+
+            model.update("hello #r", "insertText", {offset: 8, atNodeEnd: true});
+
+            expect(renderer.count).toBe(1);
+            expect(renderer.caret.index).toBe(1);
+            expect(renderer.caret.offset).toBe(2);
+            expect(model.parts.length).toBe(2);
+            expect(model.parts[0].type).toBe("plain");
+            expect(model.parts[0].text).toBe("hello ");
+            expect(model.parts[1].type).toBe("pill-candidate");
+            expect(model.parts[1].text).toBe("#r");
+
+            model.autoComplete.tryComplete();
+
+            expect(renderer.count).toBe(2);
+            expect(renderer.caret.index).toBe(1);
+            expect(renderer.caret.offset).toBe(9);
+            expect(model.parts.length).toBe(2);
+            expect(model.parts[0].type).toBe("plain");
+            expect(model.parts[0].text).toBe("hello ");
+            expect(model.parts[1].type).toBe("room-pill");
+            expect(model.parts[1].text).toBe("#riot-dev");
+        });
+        // paste circumvents AC
+    });
+});