fix(stats): elect trusted mileage source

go/vehicle-gateway/cmd/stats-backfill/main_test.go

@@ -0,0 +1,40 @@
+package main
+
+import "testing"
+
+func TestChooseTrustedSourceKeepsContinuingSourceAndRejectsNewJump(t *testing.T) {
+	previous := []dailySourceLast{{
+		VIN:            "LA9GG64L7PBAF4001",
+		SourceKey:      normalizedSourceKey("13307765812", "115.231.168.135:42630"),
+		Phone:          "13307765812",
+		SourceEndpoint: "115.231.168.135:42630",
+		TotalKM:        4100.8,
+	}}
+	current := []dailySourceLast{
+		{
+			VIN:            "LA9GG64L7PBAF4001",
+			SourceKey:      normalizedSourceKey("13307765812", "115.159.85.149:28316"),
+			Phone:          "13307765812",
+			SourceEndpoint: "115.159.85.149:28316",
+			TotalKM:        42447.2,
+		},
+		{
+			VIN:            "LA9GG64L7PBAF4001",
+			SourceKey:      normalizedSourceKey("13307765812", "115.231.168.135:20215"),
+			Phone:          "13307765812",
+			SourceEndpoint: "115.231.168.135:20215",
+			TotalKM:        4123.9,
+		},
+	}
+
+	chosen, ok := chooseTrustedSource(current, previous)
+	if !ok {
+		t.Fatal("chooseTrustedSource() did not choose a source")
+	}
+	if chosen.current.SourceKey != normalizedSourceKey("13307765812", "115.231.168.135:20215") {
+		t.Fatalf("chosen source = %q", chosen.current.SourceKey)
+	}
+	if delta := chosen.current.TotalKM - chosen.previous.TotalKM; delta < 23 || delta > 24 {
+		t.Fatalf("delta = %v, want about 23.1", delta)
+	}
+}