txmeta: fix JSON confirmations value when unconfirmed, add test

lib/primitives/txmeta.js

@@ -161,7 +161,7 @@ class TXMeta {
     json.time = this.time;
     json.confirmations = 0;
 
-    if (chainHeight != null)
+    if (chainHeight != null && this.height !== -1)
       json.confirmations = chainHeight - this.height + 1;
 
     return json;

test/txmeta-test.js

@@ -0,0 +1,26 @@
+/* eslint-env mocha */
+/* eslint prefer-arrow-callback: "off" */
+
+'use strict';
+
+const assert = require('./util/assert');
+const Network = require('../lib/protocol/network');
+const TXMeta = require('../lib/primitives/txmeta');
+
+const network = Network.get('regtest');
+
+
+describe('TXMeta', function() {
+  it('should return JSON for txmeta', async () => {
+    // unconfirmed at height 100
+    const txmeta1 = new TXMeta();
+    const txJSON1 = txmeta1.getJSON(network, null, 100)
+    assert.strictEqual(txJSON1.confirmations, 0);
+
+    // confirmed once at height 100
+    const txmeta2 = TXMeta.fromOptions( {height: 100} );
+    txmeta2.height = 100;
+    const txJSON2 = txmeta2.getJSON(network, null, 100)
+    assert.strictEqual(txJSON2.confirmations, 1);
+  });
+});