Add relationship between bill and billing account

app/models/bill.model.js

@@ -16,6 +16,14 @@ class BillModel extends BaseModel {
 
   static get relationMappings () {
     return {
+      billingAccount: {
+        relation: Model.BelongsToOneRelation,
+        modelClass: 'billing-account.model',
+        join: {
+          from: 'bills.billingAccountId',
+          to: 'billingAccounts.id'
+        }
+      },
       billRun: {
         relation: Model.BelongsToOneRelation,
         modelClass: 'bill-run.model',

app/models/billing-account.model.js

@@ -24,6 +24,14 @@ class BillingAccountModel extends BaseModel {
           to: 'billingAccountAddresses.billingAccountId'
         }
       },
+      bills: {
+        relation: Model.HasManyRelation,
+        modelClass: 'bill.model',
+        join: {
+          from: 'billingAccounts.id',
+          to: 'bills.billingAccountId'
+        }
+      },
       chargeVersions: {
         relation: Model.HasManyRelation,
         modelClass: 'charge-version.model',

test/models/bill.model.test.js

@@ -8,8 +8,10 @@ const { describe, it, beforeEach } = exports.lab = Lab.script()
 const { expect } = Code
 
 // Test helpers
-const BillRunModel = require('../../app/models/bill-run.model.js')
 const BillHelper = require('../support/helpers/bill.helper.js')
+const BillingAccountHelper = require('../support/helpers/billing-account.helper.js')
+const BillingAccountModel = require('../../app/models/billing-account.model.js')
+const BillRunModel = require('../../app/models/bill-run.model.js')
 const BillLicenceHelper = require('../support/helpers/bill-licence.helper.js')
 const BillLicenceModel = require('../../app/models/bill-licence.model.js')
 const BillRunHelper = require('../support/helpers/bill-run.helper.js')
@@ -39,6 +41,36 @@ describe('Bill model', () => {
   })
 
   describe('Relationships', () => {
+    describe('when linking to billing account', () => {
+      let testBillingAccount
+
+      beforeEach(async () => {
+        testBillingAccount = await BillingAccountHelper.add()
+
+        const { id: billingAccountId } = testBillingAccount
+        testRecord = await BillHelper.add({ billingAccountId })
+      })
+
+      it('can successfully run a related query', async () => {
+        const query = await BillModel.query()
+          .innerJoinRelated('billingAccount')
+
+        expect(query).to.exist()
+      })
+
+      it('can eager load the billing account', async () => {
+        const result = await BillModel.query()
+          .findById(testRecord.id)
+          .withGraphFetched('billingAccount')
+
+        expect(result).to.be.instanceOf(BillModel)
+        expect(result.id).to.equal(testRecord.id)
+
+        expect(result.billingAccount).to.be.an.instanceOf(BillingAccountModel)
+        expect(result.billingAccount).to.equal(testBillingAccount)
+      })
+    })
+
     describe('when linking to bill run', () => {
       let testBillRun
 

test/models/billing-account.model.test.js

@@ -8,6 +8,8 @@ const { describe, it, beforeEach } = exports.lab = Lab.script()
 const { expect } = Code
 
 // Test helpers
+const BillHelper = require('../support/helpers/bill.helper.js')
+const BillModel = require('../../app/models/bill.model.js')
 const BillingAccountAddressHelper = require('../support/helpers/billing-account-address.helper.js')
 const BillingAccountAddressModel = require('../../app/models/billing-account-address.model.js')
 const BillingAccountHelper = require('../support/helpers/billing-account.helper.js')
@@ -80,6 +82,42 @@ describe('Billing Account model', () => {
       })
     })
 
+    describe('when linking to bills', () => {
+      let testBills
+
+      beforeEach(async () => {
+        testRecord = await BillingAccountHelper.add()
+        const { id: billingAccountId } = testRecord
+
+        testBills = []
+        for (let i = 0; i < 2; i++) {
+          const bill = await BillHelper.add({ billingAccountId })
+          testBills.push(bill)
+        }
+      })
+
+      it('can successfully run a related query', async () => {
+        const query = await BillingAccountModel.query()
+          .innerJoinRelated('bills')
+
+        expect(query).to.exist()
+      })
+
+      it('can eager load the bills', async () => {
+        const result = await BillingAccountModel.query()
+          .findById(testRecord.id)
+          .withGraphFetched('bills')
+
+        expect(result).to.be.instanceOf(BillingAccountModel)
+        expect(result.id).to.equal(testRecord.id)
+
+        expect(result.bills).to.be.an.array()
+        expect(result.bills[0]).to.be.an.instanceOf(BillModel)
+        expect(result.bills).to.include(testBills[0])
+        expect(result.bills).to.include(testBills[1])
+      })
+    })
+
     describe('when linking to charge versions', () => {
       let testChargeVersions