pkg/fuzzer: factor out the fuzzing engine

This is the first step for #1541.

Move the fuzzing engine that used to be interleaved with other syz-fuzzer
code into a separate package.

For now, the algorithm is more or less the same as it was, the only
difference is that a pkg/fuzzer instance scales to the available
computing power.

Add an executor-based test that performs real fuzzing.

1 files changed, 44 insertions, 0 deletions

diff --git a/pkg/fuzzer/prio_queue_test.go b/pkg/fuzzer/prio_queue_test.go
new file mode 100644
index 000000000..b2abdb01b
--- /dev/null
+++ b/pkg/fuzzer/prio_queue_test.go
@@ -0,0 +1,44 @@
+// Copyright 2024 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package fuzzer
+
+import (
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPriority(t *testing.T) {
+	assert.True(t, priority{1, 2}.greaterThan(priority{1, 1}))
+	assert.True(t, priority{3, 2}.greaterThan(priority{2, 3}))
+	assert.True(t, priority{1, -5}.greaterThan(priority{1, -10}))
+}
+
+func TestPrioQueueOrder(t *testing.T) {
+	pq := makePriorityQueue[int]()
+	pq.push(&priorityQueueItem[int]{value: 1, prio: priority{1}})
+	pq.push(&priorityQueueItem[int]{value: 3, prio: priority{3}})
+	pq.push(&priorityQueueItem[int]{value: 2, prio: priority{2}})
+
+	assert.Equal(t, 3, pq.pop().value)
+	assert.Equal(t, 2, pq.pop().value)
+	assert.Equal(t, 1, pq.pop().value)
+	assert.Nil(t, pq.tryPop())
+}
+
+func TestPrioQueueWait(t *testing.T) {
+	var wg sync.WaitGroup
+	pq := makePriorityQueue[int]()
+	assert.Nil(t, pq.tryPop())
+
+	wg.Add(1)
+	go func() {
+		assert.Equal(t, 10, pq.pop().value)
+		wg.Done()
+	}()
+
+	pq.push(&priorityQueueItem[int]{value: 10, prio: priority{1}})
+	wg.Wait()
+}