test: add test for threshold

packages/vx-threshold/test/Threshold.test.tsx

@@ -1,7 +1,66 @@
+import React from 'react';
+import { render } from 'enzyme';
 import { Threshold } from '../src';
 
-describe('Threshold', () => {
-  test('it should be defined', () => {
+const data = [
+  { x: 1, y0: 6, y1: 10 },
+  { x: 2, y0: 7, y1: 11 },
+];
+
+describe('<Threshold />', () => {
+  it('should be defined', () => {
     expect(Threshold).toBeDefined();
   });
+
+  it('should render the path', () => {
+    const wrapper = render(
+      <svg>
+        <Threshold
+          id={`${Math.random()}`}
+          data={data}
+          x={d => d.x}
+          y0={d => d.y0}
+          y1={d => d.y1}
+          clipAboveTo={0}
+          clipBelowTo={100}
+          belowAreaProps={{
+            fill: 'violet',
+            fillOpacity: 0.4,
+          }}
+          aboveAreaProps={{
+            fill: 'green',
+            fillOpacity: 0.4,
+          }}
+        />
+      </svg>,
+    );
+    expect(wrapper.find('g.vx-threshold')).toHaveLength(1);
+    expect(wrapper.find('path')).toHaveLength(4);
+  });
+
+  it('supports accessors for clipping', () => {
+    const wrapper = render(
+      <svg>
+        <Threshold
+          id={`${Math.random()}`}
+          data={data}
+          x={d => d.x}
+          y0={d => d.y0}
+          y1={d => d.y1}
+          clipAboveTo={() => 0}
+          clipBelowTo={() => 100}
+          belowAreaProps={{
+            fill: 'violet',
+            fillOpacity: 0.4,
+          }}
+          aboveAreaProps={{
+            fill: 'green',
+            fillOpacity: 0.4,
+          }}
+        />
+      </svg>,
+    );
+    expect(wrapper.find('g.vx-threshold')).toHaveLength(1);
+    expect(wrapper.find('path')).toHaveLength(4);
+  });
 });

packages/vx-zoom/test/Zoom.test.tsx

@@ -2,7 +2,7 @@ import React from 'react';
 import { render } from 'enzyme';
 import { Zoom, inverseMatrix } from '../src';
 
-describe('Zoom', () => {
+describe('<Zoom />', () => {
   it('should be defined', () => {
     expect(Zoom).toBeDefined();
   });