Add MockPlatform which mocks Platform interface (#6)

* Add MockPlatform which mocks Platform interface

It allows an unit test to control clocks.

For usages, see noxworld-dev/opennox#698

---------

Co-authored-by: Denys Smirnov <dennwc@protonmail.com>

noxtest/test_platform.go

@@ -0,0 +1,32 @@
+package noxtest
+
+import (
+	"time"
+)
+
+// MockPlatform is a mock Platform implementation to allow test using ticks
+type MockPlatform struct {
+	T time.Duration
+}
+
+func (p *MockPlatform) Ticks() time.Duration {
+	return p.T
+}
+
+func (p *MockPlatform) Sleep(dt time.Duration) {
+	p.T += dt
+}
+
+func (p *MockPlatform) TimeSeed() int64 {
+	return 0
+}
+
+func (p *MockPlatform) RandInt() int {
+	return 0
+}
+
+func (p *MockPlatform) RandSeed(seed int64) {
+}
+
+func (p *MockPlatform) RandSeedTime() {
+}