diff --git a/lib/server.js b/lib/server.js
index 0b43c3c..ee5b583 100644
--- a/lib/server.js
+++ b/lib/server.js
@@ -119,8 +119,8 @@ WalletService.prototype.createWallet = function(opts, cb) {
 
   try {
     pubKey = new PublicKey.fromString(opts.pubKey);
-  } catch (e) {
-    return cb(e.toString());
+  } catch (ex) {
+    return cb(new ClientError('Invalid public key'));
   };
 
   var wallet = Wallet.create({
@@ -512,6 +512,9 @@ WalletService.prototype.createTx = function(opts, cb) {
       if (toAddress.network != wallet.getNetworkName())
         return cb(new ClientError('INVALIDADDRESS', 'Incorrect address network'));
 
+      if (opts.amount <= 0)
+        return cb(new ClientError('Invalid amount'));
+
       if (opts.amount < Bitcore.Transaction.DUST_AMOUNT)
         return cb(new ClientError('DUSTAMOUNT', 'Amount below dust threshold'));
 
@@ -538,8 +541,7 @@ WalletService.prototype.createTx = function(opts, cb) {
         try {
           self._selectUtxos(txp, utxos);
         } catch (ex) {
-          console.log('[server.js.523:ex:]', ex); //TODO
-          return cb(new ClientError(ex));
+          return cb(new ClientError(ex.toString()));
         }
 
         if (!txp.inputs)
diff --git a/test/integration/server.js b/test/integration/server.js
index 4c55b6a..990704d 100644
--- a/test/integration/server.js
+++ b/test/integration/server.js
@@ -302,7 +302,7 @@ describe('Copay server', function() {
       };
       server.createWallet(opts, function(err, walletId) {
         should.not.exist(walletId);
-        err.should.exist;
+        should.exist(err);
         err.message.should.contain('name');
         done();
       });
@@ -346,7 +346,20 @@ describe('Copay server', function() {
       });
     });
 
-    it.skip('should fail to create wallet with invalid pubKey argument', function(done) {});
+    it('should fail to create wallet with invalid pubKey argument', function(done) {
+      var opts = {
+        name: 'my wallet',
+        m: 2,
+        n: 3,
+        pubKey: 'dummy',
+      };
+      server.createWallet(opts, function(err, walletId) {
+        should.not.exist(walletId);
+        should.exist(err);
+        err.message.should.contain('Invalid public key');
+        done();
+      });
+    });
   });
 
   describe('#joinWallet', function() {
@@ -399,7 +412,7 @@ describe('Copay server', function() {
       };
       server.joinWallet(copayerOpts, function(err, result) {
         should.not.exist(result);
-        err.should.exist;
+        should.exist(err);
         err.message.should.contain('name');
         done();
       });
@@ -453,7 +466,39 @@ describe('Copay server', function() {
       });
     });
 
-    it.skip('should fail two wallets with same xPubKey', function(done) {});
+    it('should fail two wallets with same xPubKey', function(done) {
+      var copayerOpts = {
+        walletId: walletId,
+        name: 'me',
+        xPubKey: TestData.copayers[0].xPubKey,
+        xPubKeySignature: TestData.copayers[0].xPubKeySignature,
+      };
+      server.joinWallet(copayerOpts, function(err) {
+        should.not.exist(err);
+
+        var walletOpts = {
+          name: 'my other wallet',
+          m: 1,
+          n: 1,
+          pubKey: TestData.keyPair.pub,
+        };
+        server.createWallet(walletOpts, function(err, walletId) {
+          should.not.exist(err);
+          copayerOpts = {
+            walletId: walletId,
+            name: 'me',
+            xPubKey: TestData.copayers[0].xPubKey,
+            xPubKeySignature: TestData.copayers[0].xPubKeySignature,
+          };
+          server.joinWallet(copayerOpts, function(err) {
+            should.exist(err);
+            err.code.should.equal('CREGISTERED');
+            err.message.should.equal('Copayer ID already registered on server');
+            done();
+          });
+        });
+      });
+    });
 
     it('should fail to join with bad formated signature', function(done) {
       var copayerOpts = {
@@ -475,7 +520,7 @@ describe('Copay server', function() {
         xPubKey: TestData.copayers[0].xPubKey[0],
       };
       server.joinWallet(copayerOpts, function(err) {
-        err.should.exist;
+        should.exist(err);
         err.message.should.contain('argument missing');
         done();
       });
@@ -583,7 +628,7 @@ describe('Copay server', function() {
     it('should not create address if unable to store it', function(done) {
       sinon.stub(server.storage, 'storeAddressAndWallet').yields('dummy error');
       server.createAddress({}, function(err, address) {
-        err.should.exist;
+        should.exist(err);
         should.not.exist(address);
 
         server.getMainAddresses({}, function(err, addresses) {
@@ -625,7 +670,7 @@ describe('Copay server', function() {
           helpers.getAuthServer(result.copayerId, function(server) {
             server.createAddress({}, function(err, address) {
               should.not.exist(address);
-              err.should.exist;
+              should.exist(err);
               err.message.should.contain('not complete');
               done();
             });
@@ -656,7 +701,7 @@ describe('Copay server', function() {
             var txOpts = helpers.createProposalOpts('18PzpUFkFZE8zKWUPvfykkTxmB9oMR8qP7', 80, null, TestData.copayers[0].privKey);
             server.createTx(txOpts, function(err, tx) {
               should.not.exist(tx);
-              err.should.exist;
+              should.exist(err);
               err.message.should.contain('not complete');
               done();
             });
@@ -714,7 +759,7 @@ describe('Copay server', function() {
 
         server.createTx(txOpts, function(err, tx) {
           should.not.exist(tx);
-          err.should.exist;
+          should.exist(err);
           err.message.should.equal('Invalid proposal signature');
           done();
         });
@@ -727,7 +772,7 @@ describe('Copay server', function() {
 
         server.createTx(txOpts, function(err, tx) {
           should.not.exist(tx);
-          err.should.exist;
+          should.exist(err);
           err.message.should.equal('Invalid proposal signature');
           done();
         });
@@ -740,7 +785,7 @@ describe('Copay server', function() {
 
         server.createTx(txOpts, function(err, tx) {
           should.not.exist(tx);
-          err.should.exist;
+          should.exist(err);
           err.code.should.equal('INVALIDADDRESS');
           err.message.should.equal('Invalid address');
           done();
@@ -762,7 +807,15 @@ describe('Copay server', function() {
       });
     });
 
-    it.skip('should fail to create tx for invalid amount', function(done) {});
+    it('should fail to create tx for invalid amount', function(done) {
+      var txOpts = helpers.createProposalOpts('18PzpUFkFZE8zKWUPvfykkTxmB9oMR8qP7', 0, null, TestData.copayers[0].privKey);
+      server.createTx(txOpts, function(err, tx) {
+        should.not.exist(tx);
+        should.exist(err);
+        err.message.should.equal('Invalid amount');
+        done();
+      });
+    });
 
     it('should fail to create tx when insufficient funds', function(done) {
       helpers.stubUtxos(server, wallet, [100], function() {
@@ -809,7 +862,22 @@ describe('Copay server', function() {
       });
     });
 
-    it.skip('should fail gracefully when bitcore throws exception on raw tx creation', function(done) {});
+    it('should fail gracefully when bitcore throws exception on raw tx creation', function(done) {
+      helpers.stubUtxos(server, wallet, [10], function() {
+        var bitcoreStub = sinon.stub(Bitcore, 'Transaction');
+        bitcoreStub.throws({
+          name: 'dummy',
+          message: 'dummy exception'
+        });
+        var txOpts = helpers.createProposalOpts('18PzpUFkFZE8zKWUPvfykkTxmB9oMR8qP7', 2, null, TestData.copayers[0].privKey);
+        server.createTx(txOpts, function(err, tx) {
+          should.exist(err);
+          err.message.should.equal('dummy exception');
+          bitcoreStub.restore();
+          done();
+        });
+      });
+    });
 
     it('should create tx when there is a pending tx and enough UTXOs', function(done) {
       helpers.stubUtxos(server, wallet, [10.1, 10.2, 10.3], function() {
@@ -897,7 +965,7 @@ describe('Copay server', function() {
     var server, wallet, txid;
 
     beforeEach(function(done) {
-      helpers.createAndJoinWallet(2, 3, function(s, w) {
+      helpers.createAndJoinWallet(2, 2, function(s, w) {
         server = s;
         wallet = w;
         helpers.stubUtxos(server, wallet, _.range(1, 9), function() {
@@ -924,22 +992,63 @@ describe('Copay server', function() {
           should.not.exist(err);
           server.getPendingTxs({}, function(err, txs) {
             should.not.exist(err);
-            var tx = txs[0];
-            tx.id.should.equal(txid);
-
-            var actors = tx.getActors();
-            actors.length.should.equal(1);
-            actors[0].should.equal(wallet.copayers[0].id);
-            var action = tx.getActionBy(wallet.copayers[0].id);
-            action.type.should.equal('reject');
-            action.comment.should.equal('some reason');
-            done();
+            txs.should.be.empty;
+            server.getTx({
+              id: txid
+            }, function(err, tx) {
+              var actors = tx.getActors();
+              actors.length.should.equal(1);
+              actors[0].should.equal(wallet.copayers[0].id);
+              var action = tx.getActionBy(wallet.copayers[0].id);
+              action.type.should.equal('reject');
+              action.comment.should.equal('some reason');
+              done();
+            });
           });
         });
       });
     });
 
-    it.skip('should fail to reject non-pending TX', function(done) {});
+    it('should fail to reject non-pending TX', function(done) {
+      async.waterfall([
+
+        function(next) {
+          server.getPendingTxs({}, function(err, txs) {
+            var tx = txs[0];
+            tx.id.should.equal(txid);
+            next();
+          });
+        },
+        function(next) {
+          server.rejectTx({
+            txProposalId: txid,
+            reason: 'some reason',
+          }, function(err) {
+            should.not.exist(err);
+            next();
+          });
+        },
+        function(next) {
+          server.getPendingTxs({}, function(err, txs) {
+            should.not.exist(err);
+            txs.should.be.empty;
+            next();
+          });
+        },
+        function(next) {
+          helpers.getAuthServer(wallet.copayers[1].id, function(server) {
+            server.rejectTx({
+              txProposalId: txid,
+              reason: 'some other reason',
+            }, function(err) {
+              should.exist(err);
+              err.code.should.equal('TXNOTPENDING');
+              done();
+            });
+          });
+        },
+      ]);
+    });
   });
 
   describe('#signTx', function() {
@@ -1095,6 +1204,57 @@ describe('Copay server', function() {
         });
       });
     });
+
+    it('should fail to sign a non-pending TX', function(done) {
+      async.waterfall([
+
+        function(next) {
+          server.rejectTx({
+            txProposalId: txid,
+            reason: 'some reason',
+          }, function(err) {
+            should.not.exist(err);
+            next();
+          });
+        },
+        function(next) {
+          helpers.getAuthServer(wallet.copayers[1].id, function(server) {
+            server.rejectTx({
+              txProposalId: txid,
+              reason: 'some reason',
+            }, function(err) {
+              should.not.exist(err);
+              next();
+            });
+          });
+        },
+        function(next) {
+          server.getPendingTxs({}, function(err, txs) {
+            should.not.exist(err);
+            txs.should.be.empty;
+            next();
+          });
+        },
+        function(next) {
+          helpers.getAuthServer(wallet.copayers[2].id, function(server) {
+            server.getTx({
+              id: txid
+            }, function(err, tx) {
+              should.not.exist(err);
+              var signatures = helpers.clientSign(tx, TestData.copayers[2].xPrivKey);
+              server.signTx({
+                txProposalId: txid,
+                signatures: signatures,
+              }, function(err) {
+                should.exist(err);
+                err.code.should.equal('TXNOTPENDING');
+                done();
+              });
+            });
+          });
+        },
+      ]);
+    });
   });
 
   describe.skip('#broadcastTx', function() {
@@ -1644,9 +1804,10 @@ describe('Copay server', function() {
     it('should allow creator to remove an signed TX by himself', function(done) {
       var signatures = helpers.clientSign(txp, TestData.copayers[0].xPrivKey);
       server.signTx({
-        txProposalId: txp[0],
+        txProposalId: txp.id,
         signatures: signatures,
       }, function(err) {
+        should.not.exist(err);
         server.removePendingTx({
           txProposalId: txp.id
         }, function(err) {
@@ -1659,7 +1820,57 @@ describe('Copay server', function() {
       });
     });
 
-    it.skip('should fail to remove non-pending TX', function(done) {});
+    it('should fail to remove non-pending TX', function(done) {
+      async.waterfall([
+
+        function(next) {
+          var signatures = helpers.clientSign(txp, TestData.copayers[0].xPrivKey);
+          server.signTx({
+            txProposalId: txp.id,
+            signatures: signatures,
+          }, function(err) {
+            should.not.exist(err);
+            next();
+          });
+        },
+        function(next) {
+          helpers.getAuthServer(wallet.copayers[1].id, function(server) {
+            server.rejectTx({
+              txProposalId: txp.id,
+            }, function(err) {
+              should.not.exist(err);
+              next();
+            });
+          });
+        },
+        function(next) {
+          helpers.getAuthServer(wallet.copayers[2].id, function(server) {
+            server.rejectTx({
+              txProposalId: txp.id,
+            }, function(err) {
+              should.not.exist(err);
+              next();
+            });
+          });
+        },
+        function(next) {
+          server.getPendingTxs({}, function(err, txs) {
+            should.not.exist(err);
+            txs.should.be.empty;
+            next();
+          });
+        },
+        function(next) {
+          server.removePendingTx({
+            txProposalId: txp.id
+          }, function(err) {
+            should.exist(err);
+            err.code.should.equal('TXNOTPENDING');
+            done();
+          });
+        },
+      ]);
+    });
 
     it('should not allow non-creator copayer to remove an unsigned TX ', function(done) {
       helpers.getAuthServer(wallet.copayers[1].id, function(server2) {