feat(gl): add immutable postgres ledger storage

domain/ledger/amount_test.go

@@ -0,0 +1,38 @@
+package ledger
+
+import "testing"
+
+func TestParseAmountCanonicalizesExactValues(t *testing.T) {
+	for input, expected := range map[string]string{
+		"0":                     "0",
+		"1":                     "1",
+		"1.2300":                "1.23",
+		"-0.000000000000000001": "-0.000000000000000001",
+		"99999999999999999999":  "99999999999999999999",
+	} {
+		amount, err := ParseAmount(input)
+		if err != nil {
+			t.Fatalf("ParseAmount(%q): %v", input, err)
+		}
+		if got := amount.String(); got != expected {
+			t.Fatalf("ParseAmount(%q) = %q, want %q", input, got, expected)
+		}
+	}
+}
+
+func TestParseAmountRejectsInvalidValues(t *testing.T) {
+	for _, input := range []string{"", "+1", "01", ".1", "1.", "1e2", "1.0000000000000000001", "123456789012345678901234567890123456789"} {
+		if _, err := ParseAmount(input); err == nil {
+			t.Fatalf("ParseAmount(%q) succeeded", input)
+		}
+	}
+}
+
+func TestAmountAdditionIsExact(t *testing.T) {
+	one, _ := ParseAmount("0.1")
+	two, _ := ParseAmount("0.2")
+	minusThree, _ := ParseAmount("-0.3")
+	if got := one.Add(two).Add(minusThree); !got.IsZero() {
+		t.Fatalf("expected exact zero, got %s", got.String())
+	}
+}