util: deadline: Add a simple test for deadline and testing

This is a simple test/example placeholder if we want to remember how to
run deadlines with contexts for testing.

util/deadline/deadline_test.go

@@ -0,0 +1,50 @@
+// Mgmt
+// Copyright (C) 2013-2023+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+// Package deadline_test has examples to test the testing deadline system.
+package deadline_test
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestSlowTest1(t *testing.T) {
+	time.Sleep(3 * time.Second)
+}
+
+func TestDeadlineTimeout1(t *testing.T) {
+	now := time.Now()
+	min := time.Second * 3 // approx min time needed for the test
+	ctx := context.Background()
+	if deadline, ok := t.Deadline(); ok {
+		d := deadline.Add(-min)
+		t.Logf("  now: %+v", now)
+		t.Logf("    d: %+v", d)
+		newCtx, cancel := context.WithDeadline(ctx, d)
+		ctx = newCtx
+		defer cancel()
+	}
+
+	select {
+	case <-ctx.Done():
+		t.Logf("  ctx: %+v", time.Now())
+		time.Sleep(min - (1 * time.Second)) // one second less for safety
+		t.Logf("sleep: %+v", time.Now())
+	}
+}