transaction_tests: Be more strict checking dust

* Don't allow off-by-one or more
* Make clear dust is coupled with minRelayTxFee
* Check rounding for odd values

1 files changed, 17 insertions, 2 deletions

diff --git a/src/test/transaction_tests.cpp b/src/test/transaction_tests.cpp
index f9423bc0de..c840f4c9fd 100644
--- a/src/test/transaction_tests.cpp
+++ b/src/test/transaction_tests.cpp
@@ -342,11 +342,26 @@ BOOST_AUTO_TEST_CASE(test_IsStandard)
     string reason;
     BOOST_CHECK(IsStandardTx(t, reason));
 
-    t.vout[0].nValue = 501; // dust
+    // Check dust with default relay fee:
+    CAmount nDustThreshold = 182 * minRelayTxFee.GetFeePerK()/1000 * 3;
+    BOOST_CHECK_EQUAL(nDustThreshold, 546);
+    // dust:
+    t.vout[0].nValue = nDustThreshold - 1;
     BOOST_CHECK(!IsStandardTx(t, reason));
+    // not dust:
+    t.vout[0].nValue = nDustThreshold;
+    BOOST_CHECK(IsStandardTx(t, reason));
 
-    t.vout[0].nValue = 2730; // not dust
+    // Check dust with odd relay fee to verify rounding:
+    // nDustThreshold = 182 * 1234 / 1000 * 3
+    minRelayTxFee = CFeeRate(1234);
+    // dust:
+    t.vout[0].nValue = 672 - 1;
+    BOOST_CHECK(!IsStandardTx(t, reason));
+    // not dust:
+    t.vout[0].nValue = 672;
     BOOST_CHECK(IsStandardTx(t, reason));
+    minRelayTxFee = CFeeRate(1000);
 
     t.vout[0].scriptPubKey = CScript() << OP_1;
     BOOST_CHECK(!IsStandardTx(t, reason));