Replace a barrel file's re-export in the Babel example

Babel compiles `export { square } from './squarer'` to a getter, which
td.replace(path) used to imitate as `undefined`. This runs that path
through a real compiler in CI.

Author: rosston

examples/babel/lib/calculator.js

@@ -2,6 +2,7 @@ import Adder from './adder'
 import Subtractor from './subtractor'
 import Multiplier from './multiplier'
 import divider from './divider'
+import { square } from './operations'
 
 export default class Calculator {
   calculate(operation, ...operands) {
@@ -16,6 +17,8 @@ export default class Calculator {
         divider.numerator.set(operands[0])
         divider.otherOptions.divisor.setThatToo(operands[1])
         return new divider.ohAndAlso.Executor().execute()
+      case 'square':
+        return square(operands[0])
     }
   }
 }

examples/babel/lib/operations.js

@@ -0,0 +1,2 @@
+// Babel compiles re-exports like this one to getters
+export { square } from './squarer'

examples/babel/lib/squarer.js

@@ -0,0 +1,3 @@
+export function square (n) {
+  throw 'not implemented!'
+}

examples/babel/test/lib/calculator-test.js

@@ -2,7 +2,7 @@ import assert from 'assert'
 import { describe, it, beforeEach, afterEach } from 'node:test'
 import { td, setup, teardown } from '../helper'
 
-let subject, Adder, Subtractor, Multiplier, divider, result
+let subject, Adder, Subtractor, Multiplier, divider, operations, result
 describe('Calculator', () => {
   describe('#calculate', () => {
     beforeEach(() => {
@@ -12,6 +12,7 @@ describe('Calculator', () => {
       Subtractor = td.replace('../../lib/subtractor')
       Multiplier = td.replace('../../lib/multiplier').default
       divider = td.replace('../../lib/divider').default
+      operations = td.replace('../../lib/operations')
       const Calculator = require('../../lib/calculator').default
       subject = new Calculator()
     })
@@ -55,5 +56,14 @@ describe('Calculator', () => {
       td.verify(divider.otherOptions.divisor.setThatToo(2))
       assert.equal(result, 'lol')
     })
+
+    it('delegates to a squarer re-exported from a barrel file', () => {
+      assert.equal(td.explain(operations.square).isTestDouble, true)
+      td.when(operations.square(3)).thenReturn('squared math!')
+
+      result = subject.calculate('square', 3)
+
+      assert.equal(result, 'squared math!')
+    })
   })
 })