Move block height estimation to its own function and test it

siac/consensuscmd.go

@@ -7,6 +7,7 @@ import (
 	"github.com/spf13/cobra"
 
 	"github.com/NebulousLabs/Sia/api"
+	"github.com/NebulousLabs/Sia/types"
 )
 
 var (
@@ -33,15 +34,21 @@ Height: %v
 Target: %v
 `, yesNo(cg.Synced), cg.CurrentBlock, cg.Height, cg.Target)
 	} else {
-		// Estimate the height of the blockchain by calculating the minutes since a
-		// known block, and dividing by 10 minutes (the block time).
-		block50000Timestamp := time.Date(2016, time.May, 11, 19, 33, 0, 0, time.UTC)
-		diff := time.Since(block50000Timestamp)
-		estimatedHeight := 50000 + (diff.Minutes() / 10)
-		estimatedProgress := float64(cg.Height) / estimatedHeight * 100
+		estimatedHeight := estimatedHeightAt(time.Now())
+		estimatedProgress := float64(cg.Height) / float64(estimatedHeight) * 100
 		fmt.Printf(`Synced: %v
 Height: %v
 Progress (estimated): %.f%%
 `, yesNo(cg.Synced), cg.Height, estimatedProgress)
 	}
 }
+
+// estimatedHeightAt returns the estimated block height for the given time.
+// Block height is estimated by calculating the minutes since a known block in
+// the past and dividing by 10 minutes (the block time).
+func estimatedHeightAt(t time.Time) types.BlockHeight {
+	block5e4Timestamp := time.Date(2016, time.May, 11, 19, 33, 0, 0, time.UTC)
+	diff := t.Sub(block5e4Timestamp)
+	estimatedHeight := 5e4 + (diff.Minutes() / 10)
+	return types.BlockHeight(estimatedHeight + 0.5) // round to the nearest block
+}

siac/consensuscmd_test.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"testing"
+	"time"
+
+	"github.com/NebulousLabs/Sia/types"
+)
+
+// TestEstimatedHeightAt tests that the expectedHeightAt function correctly
+// estimates the blockheight (and rounds to the nearest block).
+func TestEstimatedHeightAt(t *testing.T) {
+	tests := []struct {
+		t              time.Time
+		expectedHeight types.BlockHeight
+	}{
+		// Test on the same block that is used to estimate the height
+		{
+			time.Date(2016, time.May, 11, 19, 33, 0, 0, time.UTC),
+			5e4,
+		},
+		// 4 minutes later
+		{
+			time.Date(2016, time.May, 11, 19, 37, 0, 0, time.UTC),
+			5e4,
+		},
+		// 5 minutes later
+		{
+			time.Date(2016, time.May, 11, 19, 38, 0, 0, time.UTC),
+			5e4 + 1,
+		},
+		// 10 minutes later
+		{
+			time.Date(2016, time.May, 11, 19, 43, 0, 0, time.UTC),
+			5e4 + 1,
+		},
+		// 1 day later
+		{
+			time.Date(2016, time.May, 12, 19, 33, 0, 0, time.UTC),
+			5e4 + 144,
+		},
+	}
+	for _, tt := range tests {
+		h := estimatedHeightAt(tt.t)
+		if h != tt.expectedHeight {
+			t.Errorf("expected an estimated height of %v, but got %v", tt.expectedHeight, h)
+		}
+	}
+}