diff --git a/Makefile b/Makefile
index ad79deb..22f134c 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@ all: clean test dists
 
 .PHONY: test
 test:
-	nosetests -v
+	pytest
 
 dists:
 	python setup.py sdist
diff --git a/dataset/database.py b/dataset/database.py
index b3ecfc2..22d1a49 100644
--- a/dataset/database.py
+++ b/dataset/database.py
@@ -93,6 +93,9 @@ class Database(object):
         """Get a SQLAlchemy inspector."""
         return inspect(self.executable)
 
+    def has_table(self, name):
+        return self.inspect.has_table(name, schema=self.schema)
+
     @property
     def metadata(self):
         """Return a SQLAlchemy schema cache object."""
diff --git a/dataset/table.py b/dataset/table.py
index c8d1948..8462f34 100644
--- a/dataset/table.py
+++ b/dataset/table.py
@@ -228,7 +228,9 @@ class Table(object):
         chunk = []
         columns = []
         for index, row in enumerate(rows):
-            columns.extend(col for col in row.keys() if (col not in columns) and (col not in keys))
+            columns.extend(
+                col for col in row.keys() if (col not in columns) and (col not in keys)
+            )
 
             # bindparam requires names to not conflict (cannot be "id" for id)
             for key in keys:
@@ -240,7 +242,7 @@ class Table(object):
             if len(chunk) == chunk_size or index == len(rows) - 1:
                 cl = [self.table.c[k] == bindparam("_%s" % k) for k in keys]
                 stmt = self.table.update(
-                    whereclause=and_(*cl),
+                    whereclause=and_(True, *cl),
                     values={col: bindparam(col, required=False) for col in columns},
                 )
                 self.db.executable.execute(stmt, chunk)
@@ -431,7 +433,7 @@ class Table(object):
                     clauses.append(self._generate_clause(column, op, op_value))
             else:
                 clauses.append(self._generate_clause(column, "=", value))
-        return and_(*clauses)
+        return and_(True, *clauses)
 
     def _args_to_order_by(self, order_by):
         orderings = []
diff --git a/dataset/util.py b/dataset/util.py
index 49512f4..1753283 100644
--- a/dataset/util.py
+++ b/dataset/util.py
@@ -14,7 +14,7 @@ class DatasetException(Exception):
 def convert_row(row_type, row):
     if row is None:
         return None
-    return row_type(row.items())
+    return row_type(row._mapping.items())
 
 
 def iter_result_proxy(rp, step=None):
diff --git a/setup.py b/setup.py
index 2631d03..518a42d 100644
--- a/setup.py
+++ b/setup.py
@@ -33,7 +33,7 @@ setup(
     extras_require={
         "dev": [
             "pip",
-            "nose",
+            "pytest",
             "wheel",
             "flake8",
             "coverage",
@@ -42,7 +42,7 @@ setup(
             "cryptography",
         ]
     },
-    tests_require=["nose"],
+    tests_require=["pytest"],
     test_suite="test",
     entry_points={},
 )
diff --git a/test/test_dataset.py b/test/test_dataset.py
index 9c2bb8e..f7c94eb 100644
--- a/test/test_dataset.py
+++ b/test/test_dataset.py
@@ -35,7 +35,7 @@ class DatabaseTestCase(unittest.TestCase):
 
     def test_create_table(self):
         table = self.db["foo"]
-        assert table.table.exists()
+        assert self.db.has_table(table.table.name)
         assert len(table.table.columns) == 1, table.table.columns
         assert "id" in table.table.c, table.table.c
 
@@ -51,7 +51,7 @@ class DatabaseTestCase(unittest.TestCase):
     def test_create_table_custom_id1(self):
         pid = "string_id"
         table = self.db.create_table("foo2", pid, self.db.types.string(255))
-        assert table.table.exists()
+        assert self.db.has_table(table.table.name)
         assert len(table.table.columns) == 1, table.table.columns
         assert pid in table.table.c, table.table.c
         table.insert({pid: "foobar"})
@@ -60,7 +60,7 @@ class DatabaseTestCase(unittest.TestCase):
     def test_create_table_custom_id2(self):
         pid = "string_id"
         table = self.db.create_table("foo3", pid, self.db.types.string(50))
-        assert table.table.exists()
+        assert self.db.has_table(table.table.name)
         assert len(table.table.columns) == 1, table.table.columns
         assert pid in table.table.c, table.table.c
 
@@ -70,7 +70,7 @@ class DatabaseTestCase(unittest.TestCase):
     def test_create_table_custom_id3(self):
         pid = "int_id"
         table = self.db.create_table("foo4", primary_id=pid)
-        assert table.table.exists()
+        assert self.db.has_table(table.table.name)
         assert len(table.table.columns) == 1, table.table.columns
         assert pid in table.table.c, table.table.c