Add 100% test coverage for new median time code.

internal_test.go

@@ -34,3 +34,9 @@ func TstTimeSorter(times []time.Time) timeSorter {
 func TstCheckSerializedHeight(coinbaseTx *btcutil.Tx, wantHeight int64) error {
 	return checkSerializedHeight(coinbaseTx, wantHeight)
 }
+
+// TstSetMaxMedianTimeEntries makes the ability to set the maximum number of
+// median tiem entries available to the test package.
+func TstSetMaxMedianTimeEntries(val int) {
+	maxMedianTimeEntries = val
+}

mediantime_test.go

@@ -0,0 +1,96 @@
+// Copyright (c) 2013-2014 Conformal Systems LLC.
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package btcchain_test
+
+import (
+	"strconv"
+	"testing"
+	"time"
+
+	"github.com/conformal/btcchain"
+)
+
+// TestMedianTime tests the medianTime implementation.
+func TestMedianTime(t *testing.T) {
+	tests := []struct {
+		in         []int64
+		wantOffset int64
+		useDupID   bool
+	}{
+		// Not enough samples must result in an offset of 0.
+		{in: []int64{1}, wantOffset: 0},
+		{in: []int64{1, 2}, wantOffset: 0},
+		{in: []int64{1, 2, 3}, wantOffset: 0},
+		{in: []int64{1, 2, 3, 4}, wantOffset: 0},
+
+		// Various number of entries.  The expected offset is only
+		// updated on odd number of elements.
+		{in: []int64{-13, 57, -4, -23, -12}, wantOffset: 12},
+		{in: []int64{55, -13, 61, -52, 39, 55}, wantOffset: -39},
+		{in: []int64{-62, -58, -30, -62, 51, -30, 15}, wantOffset: 30},
+		{in: []int64{29, -47, 39, 54, 42, 41, 8, -33}, wantOffset: -39},
+		{in: []int64{37, 54, 9, -21, -56, -36, 5, -11, -39}, wantOffset: 11},
+		{in: []int64{57, -28, 25, -39, 9, 63, -16, 19, -60, 25}, wantOffset: -9},
+		{in: []int64{-5, -4, -3, -2, -1}, wantOffset: 3, useDupID: true},
+
+		// The offset stops being updated once the max number of entries
+		// has been reached.  This is actually a bug from Bitcoin Core,
+		// but since the time is ultimately used as a part of the
+		// consensus rules, it must be mirrored.
+		{in: []int64{-67, 67, -50, 24, 63, 17, 58, -14, 5, -32, -52}, wantOffset: -17},
+		{in: []int64{-67, 67, -50, 24, 63, 17, 58, -14, 5, -32, -52, 45}, wantOffset: -17},
+		{in: []int64{-67, 67, -50, 24, 63, 17, 58, -14, 5, -32, -52, 45, 4}, wantOffset: -17},
+
+		// Offsets that are too far away from the local time should
+		// be ignored.
+		{in: []int64{-4201, 4202, -4203, 4204, -4205}, wantOffset: 0},
+
+		// Excerise the condition where the median offset is greater
+		// than the max allowed adjustment, but there is at least one
+		// sample that is close enough to the current time to avoid
+		// triggering a warning about an invalid local clock.
+		{in: []int64{4201, 4202, 4203, 4204, -299}, wantOffset: 0},
+	}
+
+	// Modify the max number of allowed median time entries for these tests.
+	btcchain.TstSetMaxMedianTimeEntries(10)
+	defer btcchain.TstSetMaxMedianTimeEntries(200)
+
+	for i, test := range tests {
+		filter := btcchain.NewMedianTime()
+		for j, offset := range test.in {
+			id := strconv.Itoa(j)
+			tOffset := time.Now().Add(time.Duration(offset) *
+				time.Second)
+			filter.AddTimeSample(id, tOffset)
+
+			// Ensure the duplicate IDs are ignored.
+			if test.useDupID {
+				// Modify the offsets to ensure the final median
+				// would be different if the duplicate is added.
+				tOffset = tOffset.Add(time.Duration(offset) *
+					time.Second)
+				filter.AddTimeSample(id, tOffset)
+			}
+		}
+
+		gotOffset := filter.Offset()
+		wantOffset := time.Duration(test.wantOffset) * time.Second
+		if gotOffset != wantOffset {
+			t.Errorf("Offset #%d: unexpected offset -- got %v, "+
+				"want %v", i, gotOffset, wantOffset)
+			continue
+		}
+
+		adjustedTime := time.Unix(filter.AdjustedTime().Unix(), 0)
+		wantTime := time.Now().Add(filter.Offset())
+		wantTime = time.Unix(wantTime.Unix(), 0)
+		if !adjustedTime.Equal(wantTime) {
+			t.Errorf("AdjustedTime #%d: unexpected result -- got %v, "+
+				"want %v", i, adjustedTime, wantTime)
+			continue
+		}
+	}
+}