Added very basic unit test coverage to cover happy path import

refs https://github.com/TryGhost/Team/issues/916

- These tests are nowhere close to perfect of even good. They barely pass "good enough" watermark... it's a start for new tests to be added easier in the future once the features are developed around CSV improrter

ghost/members-importer/test/fixtures/single-column-with-header.csv

@@ -0,0 +1,3 @@
+email
+jbloggs@example.com
+test@example.com

ghost/members-importer/test/importer.test.js

@@ -0,0 +1,102 @@
+// Switch these lines once there are useful utils
+// const testUtils = require('./utils');
+require('./utils');
+
+const path = require('path');
+const sinon = require('sinon');
+const MembersCSVImporter = require('..');
+
+const csvPath = path.join(__dirname, '/fixtures/');
+
+describe('Importer', function () {
+    describe('process', function () {
+        it('should import a CSV file', async function () {
+            const defaultProduct = {
+                id: 'default_product_id'
+            };
+
+            const membersApi = {
+                productRepository: {
+                    list: async () => {
+                        return {
+                            data: [defaultProduct]
+                        };
+                    }
+                },
+                members: {
+                    get: async () => {
+                        return null;
+                    },
+                    create: async (row) => {
+                        return row;
+                    }
+                }
+            };
+
+            const knexStub = {
+                transaction: sinon.stub().resolves({
+                    rollback: () => {},
+                    commit: () => {}
+                })
+            };
+
+            const LabelModelStub = {
+                findOne: sinon.stub().resolves(null)
+            };
+
+            const importer = new MembersCSVImporter({
+                storagePath: csvPath,
+                getTimezone: sinon.stub().returns('UTC'),
+                getMembersApi: () => membersApi,
+                sendEmail: sinon.stub(),
+                isSet: sinon.stub(),
+                addJob: sinon.stub(),
+                knex: knexStub,
+                urlFor: sinon.stub()
+            });
+
+            const result = await importer.process({
+                pathToCSV: `${csvPath}/single-column-with-header.csv`,
+                headerMapping: {},
+                importLabel: {
+                    name: 'test import'
+                },
+                user: {
+                    email: 'test@example.com'
+                },
+                LabelModel: LabelModelStub
+            });
+
+            should.exist(result.meta);
+            should.exist(result.meta.stats);
+            should.exist(result.meta.stats.imported);
+            result.meta.stats.imported.should.equal(2);
+
+            should.exist(result.meta.stats.invalid);
+            should.equal(result.meta.import_label, null);
+        });
+    });
+
+    describe('prepare', function () {
+        it('processes a basic valid import file for members', async function () {
+            const membersImporter = new MembersCSVImporter({
+                storagePath: csvPath,
+                getTimezone: sinon.stub().returns('UTC'),
+                getMembersApi: sinon.stub(),
+                sendEmail: sinon.stub(),
+                isSet: sinon.stub(),
+                addJob: sinon.stub(),
+                knex: sinon.stub(),
+                urlFor: sinon.stub()
+            });
+
+            const result = await membersImporter.prepare(`${csvPath}/single-column-with-header.csv`);
+
+            should.exist(result.id);
+            result.id.should.match(/\/members-importer\/test\/fixtures\/Members Import/);
+
+            result.batches.should.equal(2);
+            should.exist(result.metadata);
+        });
+    });
+});