test: getAbsolute* (#33)

Namely:
- getAbsoluteTop,
- getAbsoluteRight,
- getAbsoluteLeft.

test/get-absolute.test.ts

@@ -0,0 +1,26 @@
+import { expect } from 'chai'
+import { stub } from 'sinon'
+
+import { getAbsoluteLeft, getAbsoluteRight, getAbsoluteTop } from '../src'
+
+describe('getAbsolute*', function(): void {
+  const elem = { getBoundingClientRect: stub() }
+  elem.getBoundingClientRect.returns({
+    top: 1,
+    right: 2,
+    bottom: 3,
+    left: 4,
+  })
+
+  it('getAbsoluteTop', function(): void {
+    expect(getAbsoluteTop(elem as any)).to.equal(1)
+  })
+
+  it('getAbsoluteRight', function(): void {
+    expect(getAbsoluteRight(elem as any)).to.equal(2)
+  })
+
+  it('getAbsoluteLeft', function(): void {
+    expect(getAbsoluteLeft(elem as any)).to.equal(4)
+  })
+})