diff --git a/src/browser/Decorations/ColorZoneStore.test.ts b/src/browser/Decorations/ColorZoneStore.test.ts
new file mode 100644
index 00000000..73e3402f
--- /dev/null
+++ b/src/browser/Decorations/ColorZoneStore.test.ts
@@ -0,0 +1,88 @@
+/**
+ * Copyright (c) 2017 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { assert } from 'chai';
+import { ColorZoneStore } from 'browser/Decorations/ColorZoneStore';
+
+const optionsRedFull = {
+  overviewRulerOptions: {
+    color: 'red',
+    position: 'full' as 'full'
+  }
+};
+
+describe('ColorZoneStore', () => {
+  let store: ColorZoneStore;
+
+  beforeEach(() => {
+    store = new ColorZoneStore();
+    store.setPadding({
+      full: 1,
+      left: 1,
+      center: 1,
+      right: 1
+    });
+  });
+
+  it('should merge adjacent zones', () => {
+    store.addDecoration({
+      marker: { line: 0 },
+      options: optionsRedFull
+    });
+    store.addDecoration({
+      marker: { line: 1 },
+      options: optionsRedFull
+    });
+    assert.deepStrictEqual(store.zones, [
+      {
+        color: 'red',
+        position: 'full',
+        startBufferLine: 0,
+        endBufferLine: 1
+      }
+    ]);
+  });
+
+  it('should not merge non-adjacent zones', () => {
+    store.addDecoration({
+      marker: { line: 0 },
+      options: optionsRedFull
+    });
+    store.addDecoration({
+      marker: { line: 2 },
+      options: optionsRedFull
+    });
+    assert.deepStrictEqual(store.zones, [
+      {
+        color: 'red',
+        position: 'full',
+        startBufferLine: 0,
+        endBufferLine: 0
+      },
+      {
+        color: 'red',
+        position: 'full',
+        startBufferLine: 2,
+        endBufferLine: 2
+      }
+    ]);
+  });
+
+  it('should reuse zone objects', () => {
+    const obj = {
+      marker: { line: 0 },
+      options: optionsRedFull
+    };
+    store.addDecoration(obj);
+    const zone = store.zones[0];
+    store.clear();
+    store.addDecoration({
+      marker: { line: 1 },
+      options: optionsRedFull
+    });
+    // The object reference should be the same
+    assert.equal(zone, store.zones[0]);
+  });
+});
diff --git a/src/browser/Decorations/ColorZoneStore.ts b/src/browser/Decorations/ColorZoneStore.ts
index bf68dc14..d066bedb 100644
--- a/src/browser/Decorations/ColorZoneStore.ts
+++ b/src/browser/Decorations/ColorZoneStore.ts
@@ -24,6 +24,11 @@ export interface IColorZone {
   endBufferLine: number;
 }
 
+interface IMinimalDecorationForColorZone {
+  marker: Pick<IInternalDecoration['marker'], 'line'>;
+  options: Pick<IInternalDecoration['options'], 'overviewRulerOptions'>;
+}
+
 export class ColorZoneStore implements IColorZoneStore {
   private _zones: IColorZone[] = [];
 
@@ -51,7 +56,7 @@ export class ColorZoneStore implements IColorZoneStore {
     this._zonePoolIndex = 0;
   }
 
-  public addDecoration(decoration: IInternalDecoration): void {
+  public addDecoration(decoration: IMinimalDecorationForColorZone): void {
     if (!decoration.options.overviewRulerOptions) {
       return;
     }
@@ -62,7 +67,6 @@ export class ColorZoneStore implements IColorZoneStore {
           return;
         }
         if (this._lineAdjacentToZone(z, decoration.marker.line, decoration.options.overviewRulerOptions.position)) {
-          console.log('add line to zone');
           this._addLineToZone(z, decoration.marker.line);
           return;
         }