More false positive prevention in new time tests.

This commit extends the same logic in the previous commit to the
comparison of offsets returned from the median time source in the tests.

In particular it modifies the tests to allow for the offsets to differ by
a second due to a boundary condition to prevent false positives.

mediantime.go

@@ -118,7 +118,8 @@ func (m *medianTime) AddTimeSample(sourceID string, timeVal time.Time) {
 	// of offsets while respecting the maximum number of allowed entries by
 	// replacing the oldest entry with the new entry once the maximum number
 	// of entries is reached.
-	offsetSecs := int64(time.Now().Sub(timeVal).Seconds())
+	now := time.Unix(time.Now().Unix(), 0)
+	offsetSecs := int64(now.Sub(timeVal).Seconds())
 	numOffsets := len(m.offsets)
 	if numOffsets == maxMedianTimeEntries && maxMedianTimeEntries > 0 {
 		m.offsets = m.offsets[1:]

mediantime_test.go

@@ -62,8 +62,8 @@ func TestMedianTime(t *testing.T) {
 		filter := btcchain.NewMedianTime()
 		for j, offset := range test.in {
 			id := strconv.Itoa(j)
-			tOffset := time.Now().Add(time.Duration(offset) *
+			now := time.Unix(time.Now().Unix(), 0)
-				time.Second)
+			tOffset := now.Add(time.Duration(offset) * time.Second)
 			filter.AddTimeSample(id, tOffset)
 
 			// Ensure the duplicate IDs are ignored.
@@ -76,11 +76,16 @@ func TestMedianTime(t *testing.T) {
 			}
 		}
 
+		// Since it is possible that the time.Now call in AddTimeSample
+		// and the time.Now calls here in the tests will be off by one
+		// second, allow a fudge factor to compensate.
 		gotOffset := filter.Offset()
 		wantOffset := time.Duration(test.wantOffset) * time.Second
-		if gotOffset != wantOffset {
+		wantOffset2 := time.Duration(test.wantOffset-1) * time.Second
+		if gotOffset != wantOffset && gotOffset != wantOffset2 {
 			t.Errorf("Offset #%d: unexpected offset -- got %v, "+
-				"want %v", i, gotOffset, wantOffset)
+				"want %v or %v", i, gotOffset, wantOffset,
+				wantOffset2)
 			continue
 		}