schedgroup: tasks heap tests

Signed-off-by: Matt Layher <mdlayher@gmail.com>

heap_test.go

@@ -0,0 +1,69 @@
+package schedgroup
+
+import (
+	"container/heap"
+	"testing"
+	"time"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func Test_tasksHeap(t *testing.T) {
+	newTask := func(d time.Duration) task {
+		return task{
+			// Static start time for consistency, no call function.
+			Deadline: time.Unix(0, 0).Add(d * time.Second),
+		}
+	}
+
+	tests := []struct {
+		name     string
+		in, want []task
+	}{
+		{
+			name: "ordered",
+			in: []task{
+				newTask(1),
+				newTask(2),
+				newTask(3),
+			},
+			want: []task{
+				newTask(1),
+				newTask(2),
+				newTask(3),
+			},
+		},
+		{
+			name: "unordered",
+			in: []task{
+				newTask(3),
+				newTask(1),
+				newTask(2),
+			},
+			want: []task{
+				newTask(1),
+				newTask(2),
+				newTask(3),
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Push and pop all tasks to verify the heap.Interface implementation.
+			var tasks tasks
+			for _, v := range tt.in {
+				heap.Push(&tasks, v)
+			}
+
+			var got []task
+			for tasks.Len() > 0 {
+				got = append(got, heap.Pop(&tasks).(task))
+			}
+
+			if diff := cmp.Diff(tt.want, got); diff != "" {
+				t.Fatalf("unexpected output tasks (-want +got):\n%s", diff)
+			}
+		})
+	}
+}