fix: BLOCKING behaviour to not return immediately

It needs to wait until the timeElapsed is greater or eq the defined blocking time.
The test was enhanced to spot the issue and verify the fix worked. This
uncovered another issue with the way found events are evaluated to always return
even without any event received. This problem is also fixed by this commit.

src/commands/xread.js

@@ -53,9 +53,12 @@ export function xread(option, ...args) {
         let timeElapsed = 0
         const f = () =>
           setTimeout(() => {
-            if (opVal > 0 && timeElapsed < opVal) return resolve(null)
+            if (opVal > 0 && timeElapsed >= opVal) return resolve(null)
             const events = pollEvents(toPoll, 1)
-            if (events.length > 0) return resolve(events)
+            // If any stream has a value return
+            if (events.find(event => event[1] && event[1].length > 0)) {
+              return resolve(events)
+            }
             timeElapsed += 100
             return f()
           }, 100)

test/integration/commands/xread.js

@@ -126,11 +126,64 @@ describe('xread', () => {
       })
   })
 
-  it('should block reads with a time out', () => {
+  it('should block reads on a stream with a time out', () => {
     const redis = new Redis()
-    return redis.xread('BLOCK', '500', 'STREAMS', 'stream', '$').then(row => {
-      expect(row).toBe(null)
-    })
+    const before = performance.now()
+    return redis
+      .xread('BLOCK', '500', 'STREAMS', 'empty-stream', '$')
+      .then(row => {
+        const after = performance.now()
+        expect(after - before >= 500).toBe(true)
+        expect(row).toBe(null)
+      })
+  })
+
+  it('should block reads on multiple streams with a time out', () => {
+    const redis = new Redis()
+    const before = performance.now()
+    return redis
+      .xread(
+        'BLOCK',
+        '500',
+        'STREAMS',
+        'empty-stream',
+        'empty-stream-2',
+        '$',
+        '$'
+      )
+      .then(row => {
+        const after = performance.now()
+        expect(after - before >= 500).toBe(true)
+        expect(row).toBe(null)
+      })
+  })
+
+  it('should block until data is provided and return', () => {
+    const redis = new Redis()
+    const before = performance.now()
+
+    setTimeout(() => {
+      return redis.xadd('empty-stream-2', '*', 'key', 'val')
+    }, 100)
+
+    return redis
+      .xread(
+        'BLOCK',
+        '500',
+        'STREAMS',
+        'empty-stream',
+        'empty-stream-2',
+        '$',
+        '$'
+      )
+      .then(row => {
+        const after = performance.now()
+        expect(after - before >= 100).toBe(true)
+        expect(row).toEqual([
+          ['empty-stream-2', [['1-0', ['key', 'val']]]],
+          ['empty-stream', []],
+        ])
+      })
   })
 
   it('should poll all events since ID if no COUNT is given', () => {