stream, test: test _readableState.emittedReadable

Part of #8683, increase coverage of the internal
state machine of streams.
PR-URL: #10249
See: #8683
See: #10230
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Author: joyeecheung

test/parallel/test-stream-readable-emittedReadable.js

@@ -0,0 +1,70 @@
+'use strict';
+constcommon=require('../common');
+constassert=require('assert');
+constReadable=require('stream').Readable;
+
+constreadable=newReadable({
+read: ()=>{}
+});
+
+// Initialized to false.
+assert.strictEqual(readable._readableState.emittedReadable,false);
+
+readable.on('readable',common.mustCall(()=>{
+// emittedReadable should be true when the readable event is emitted
+assert.strictEqual(readable._readableState.emittedReadable,true);
+readable.read();
+// emittedReadable is reset to false during read()
+assert.strictEqual(readable._readableState.emittedReadable,false);
+},4));
+
+// When the first readable listener is just attached,
+// emittedReadable should be false
+assert.strictEqual(readable._readableState.emittedReadable,false);
+
+// Each one of these should trigger a readable event.
+process.nextTick(common.mustCall(()=>{
+readable.push('foo');
+}));
+process.nextTick(common.mustCall(()=>{
+readable.push('bar');
+}));
+process.nextTick(common.mustCall(()=>{
+readable.push('quo');
+}));
+process.nextTick(common.mustCall(()=>{
+readable.push(null);
+}));
+
+constnoRead=newReadable({
+read: ()=>{}
+});
+
+noRead.on('readable',common.mustCall(()=>{
+// emittedReadable should be true when the readable event is emitted
+assert.strictEqual(noRead._readableState.emittedReadable,true);
+noRead.read(0);
+// emittedReadable is not reset during read(0)
+assert.strictEqual(noRead._readableState.emittedReadable,true);
+}));
+
+noRead.push('foo');
+noRead.push(null);
+
+constflowing=newReadable({
+read: ()=>{}
+});
+
+flowing.on('data',common.mustCall(()=>{
+// When in flowing mode, emittedReadable is always false.
+assert.strictEqual(flowing._readableState.emittedReadable,false);
+flowing.read();
+assert.strictEqual(flowing._readableState.emittedReadable,false);
+},3));
+
+flowing.push('foooo');
+flowing.push('bar');
+flowing.push('quo');
+process.nextTick(common.mustCall(()=>{
+flowing.push(null);
+}));