Add testing for promise specific usage

Author: Bluenix2

packages/pg-cursor/test/promises.js

@@ -0,0 +1,60 @@
+const assert = require('assert')
+const Cursor = require('../')
+const pg = require('pg')
+
+const text = 'SELECT generate_series as num FROM generate_series(0, 5)'
+
+describe('cursor using promises', function () {
+  beforeEach(function (done) {
+    const client = (this.client = new pg.Client())
+    client.connect(done)
+
+    this.pgCursor = function (text, values) {
+      return client.query(new Cursor(text, values || []))
+    }
+  })
+
+  afterEach(function () {
+    this.client.end()
+  })
+
+  it('resolve with result', function (done) {
+    const cursor = this.pgCursor(text)
+    cursor
+      .read(6)
+      .then((res) => assert.strictEqual(res.length, 6))
+      .error((err) => assert.ifError(err))
+      .finally(() => done())
+  })
+
+  it('reject with error', function (done) {
+    const cursor = this.pgCursor('select asdfasdf')
+    cursor.read(1).error((err) => {
+      assert(err)
+      done()
+    })
+  })
+
+  it('read multiple times', async function (done) {
+    const cursor = this.pgCursor(text)
+    let res
+
+    try {
+      res = await cursor.read(2)
+      assert.strictEqual(res.length, 2)
+
+      res = await cursor.read(3)
+      assert.strictEqual(res.length, 3)
+
+      res = await cursor.read(1)
+      assert.strictEqual(res.length, 1)
+
+      res = await cursor.read(1)
+      assert.strictEqual(res.length, 0)
+    } catch (err) {
+      assert.ifError(err)
+    } finally {
+      done()
+    }
+  })
+})