test: ENG-03 share behavior fixtures across source and releases

test/contracts/emitter.js

@@ -0,0 +1,61 @@
+import assert from 'node:assert/strict'
+
+export const emitterContracts = {
+  'EVENT.chain-context-arguments': function (Emitter) {
+    const emitter = new Emitter()
+    const context = {}
+    const payload = {}
+    let observed
+    assert.equal(emitter.on('value', function (...args) {
+      observed = { context: this, args }
+    }, context), emitter)
+    assert.equal(emitter.emit('value', payload, 42), emitter)
+    assert.equal(observed.context, context)
+    assert.deepEqual(observed.args, [payload, 42])
+    assert.equal(emitter.off('value'), emitter)
+  },
+  'EVENT.once-reentry': function (Emitter) {
+    const emitter = new Emitter()
+    let calls = 0
+    emitter.once('value', () => {
+      calls++
+      emitter.emit('value')
+    })
+    emitter.emit('value').emit('value')
+    assert.equal(calls, 1)
+  },
+  'EVENT.dispatch-snapshot': function (Emitter) {
+    const emitter = new Emitter()
+    const trace = []
+    const second = () => trace.push('second')
+    const later = () => trace.push('later')
+    emitter.on('value', () => {
+      trace.push('first')
+      emitter.off('value', second)
+      emitter.on('value', later)
+    }).on('value', second)
+    emitter.emit('value').emit('value')
+    assert.deepEqual(trace, ['first', 'second', 'first', 'later'])
+  },
+  'EVENT.off-original-once': function (Emitter) {
+    const emitter = new Emitter()
+    let calls = 0
+    const listener = () => calls++
+    emitter.once('value', listener).off('value', listener).emit('value')
+    assert.equal(calls, 0)
+    emitter.on('value', listener).on('value', listener).off('value', listener).emit('value')
+    assert.equal(calls, 0)
+  },
+  'EVENT.throw-propagation': function (Emitter) {
+    const emitter = new Emitter()
+    const marker = new Error('listener failed')
+    let later = false
+    emitter.on('value', () => {
+      throw marker
+    }).on('value', () => {
+      later = true
+    })
+    assert.throws(() => emitter.emit('value'), error => error === marker)
+    assert.equal(later, false)
+  },
+}