diff --git a/tes/client.py b/tes/client.py
index d3f21a7..5539a34 100644
--- a/tes/client.py
+++ b/tes/client.py
@@ -193,14 +193,14 @@ class HTTPClient(object):
             time.sleep(0.5)
 
     def _request_params(
-        self, data: Optional[str] = None,
-        params: Optional[Dict] = None
+        self, data: Optional[str] = None, params: Optional[Dict] = None
     ) -> Dict[str, Any]:
         kwargs: Dict[str, Any] = {}
         kwargs['timeout'] = self.timeout
         kwargs['headers'] = {}
         kwargs['headers']['Content-type'] = 'application/json'
-        kwargs['auth'] = (self.user, self.password)
+        if self.user is not None and self.password is not None:
+            kwargs['auth'] = (self.user, self.password)
         if data:
             kwargs['data'] = data
         if params:
diff --git a/tes/models.py b/tes/models.py
index 8550291..09804cd 100644
--- a/tes/models.py
+++ b/tes/models.py
@@ -10,19 +10,15 @@ from datetime import datetime
 from typing import Any, Dict, List, Optional, Tuple, Type, Union
 
 
-@attrs
+@attrs(repr=False)
 class _ListOfValidator(object):
     type: Type = attrib()
 
-    def __call__(self, inst, attr, value):
-        """
-        We use a callable class to be able to change the ``__repr__``.
-        """
+    def __call__(self, inst, attr, value) -> None:
         if not all([isinstance(n, self.type) for n in value]):
             raise TypeError(
-                "'{attr.name}' must be a list of {self.type!r} (got {value!r} "
-                "that is a list of {values[0].__class__!r}).",
-                attr, self.type, value,
+                f"'{attr.name}' must be a list of {self.type!r} (got "
+                f"{value!r}", attr
             )
 
     def __repr__(self) -> str:
@@ -60,15 +56,15 @@ def strconv(value: Any) -> Any:
 # since an int64 value is encoded as a string in json we need to handle
 # conversion
 def int64conv(value: Optional[str]) -> Optional[int]:
-    if value is not None:
-        return int(value)
-    return value
+    if value is None:
+        return value
+    return int(value)
 
 
 def timestampconv(value: Optional[str]) -> Optional[datetime]:
-    if value is not None:
-        return dateutil.parser.parse(value)
-    return value
+    if value is None:
+        return value
+    return dateutil.parser.parse(value)
 
 
 def datetime_json_handler(x: Any) -> str:
@@ -294,7 +290,7 @@ class Task(Base):
             for e in self.executors:
                 if e.image is None:
                     errs.append("Executor image must be provided")
-                if len(e.command) == 0:
+                if e.command is None or len(e.command) == 0:
                     errs.append("Executor command must be provided")
                 if e.stdin is not None:
                     if not os.path.isabs(e.stdin):
@@ -306,8 +302,8 @@ class Task(Base):
                     if not os.path.isabs(e.stderr):
                         errs.append("Executor stderr must be an absolute path")
                 if e.env is not None:
-                    for k, v in e.env:
-                        if not isinstance(k, str) and not isinstance(k, str):
+                    for k, v in e.env.items():
+                        if not isinstance(k, str) and not isinstance(v, str):
                             errs.append(
                                 "Executor env keys and values must be StrType"
                             )
@@ -339,7 +335,7 @@ class Task(Base):
                         errs.append("Volume paths must be absolute")
 
         if self.tags is not None:
-            for k, v in self.tags:
+            for k, v in self.tags.items():
                 if not isinstance(k, str) and not isinstance(k, str):
                     errs.append(
                         "Tag keys and values must be StrType"
diff --git a/tes/utils.py b/tes/utils.py
index 199543b..8587d5f 100644
--- a/tes/utils.py
+++ b/tes/utils.py
@@ -27,14 +27,20 @@ class TimeoutError(Exception):
 
 
 def unmarshal(j: Any, o: Type, convert_camel_case=True) -> Any:
+    m: Any = None
     if isinstance(j, str):
-        m = json.loads(j)
-    elif isinstance(j, dict):
-        m = j
+        try:
+            m = json.loads(j)
+        except json.decoder.JSONDecodeError:
+            pass
     elif j is None:
         return None
     else:
-        raise TypeError("j must be a str, a dict or None")
+        m = j
+
+    if not isinstance(m, dict):
+        raise TypeError("j must be a dictionary, a JSON string evaluation to "
+                        "a dictionary, or None")
 
     d: Dict[str, Any] = {}
     if convert_camel_case:
@@ -77,16 +83,8 @@ def unmarshal(j: Any, o: Type, convert_camel_case=True) -> Any:
         field = v
         omap = fullOmap.get(o.__name__, {})
         if k in omap:
-            if isinstance(omap[k], tuple):
-                try:
-                    obj = omap[k][0]
-                    field = _unmarshal(v, obj)
-                except Exception:
-                    obj = omap[k][1]
-                    field = _unmarshal(v, obj)
-            else:
-                obj = omap[k]
-                field = _unmarshal(v, obj)
+            obj = omap[k]
+            field = _unmarshal(v, obj)
         r[k] = field
 
     try:

diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index e01138f..b273973 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -29,7 +29,12 @@ jobs:
         run: pip install .
 
       - name: Lint with Flake8
-        run: flake8 .
+        run: flake8 --max-line-length=120 .
 
       - name: Run unit tests
-        run: coverage run --source tes -m pytest -W ignore::DeprecationWarning
+        run: |
+          pytest \
+            --cov=tes/ \
+            --cov-branch \
+            --cov-report=term-missing \
+            --cov-fail-under=99
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/requirements.txt b/tests/requirements.txt
index 45208ca..8f67ab0 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -2,4 +2,5 @@ coverage>=6.5.0
 coveralls>=3.3.1
 flake8>=5.0.4
 pytest>=7.2.1
+pytest-cov>=4.0.0
 requests_mock>=1.10.0
diff --git a/tests/test_client.py b/tests/test_client.py
index 08b2448..52ade42 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -53,7 +53,7 @@ class TestHTTPClient(unittest.TestCase):
             )
             self.cli.create_task(self.task)
             self.assertEqual(m.last_request.text, self.task.as_json())
-            self.assertEqual(m.last_request.timeout, self.cli.timeout)
+            self.assertAlmostEqual(m.last_request.timeout, self.cli.timeout)
 
             m.post(
                 "%s/ga4gh/tes/v1/tasks" % (self.mock_url),
@@ -62,6 +62,9 @@ class TestHTTPClient(unittest.TestCase):
             with self.assertRaises(requests.HTTPError):
                 self.cli.create_task(self.task)
 
+            with self.assertRaises(TypeError):
+                self.cli.create_task('not_a_task_object')  # type: ignore
+
     def test_get_task(self):
         with requests_mock.Mocker() as m:
             m.get(
@@ -79,7 +82,7 @@ class TestHTTPClient(unittest.TestCase):
                     self.mock_url, self.mock_id
                 )
             )
-            self.assertEqual(m.last_request.timeout, self.cli.timeout)
+            self.assertAlmostEqual(m.last_request.timeout, self.cli.timeout)
 
             m.get(
                 requests_mock.ANY,
@@ -102,7 +105,7 @@ class TestHTTPClient(unittest.TestCase):
                 m.last_request.url,
                 "%s/ga4gh/tes/v1/tasks?view=MINIMAL" % (self.mock_url)
             )
-            self.assertEqual(m.last_request.timeout, self.cli.timeout)
+            self.assertAlmostEqual(m.last_request.timeout, self.cli.timeout)
 
             # empty response
             m.get(
@@ -137,7 +140,7 @@ class TestHTTPClient(unittest.TestCase):
                 "%s/ga4gh/tes/v1/tasks/%s:cancel" % (
                     self.mock_url, self.mock_id)
             )
-            self.assertEqual(m.last_request.timeout, self.cli.timeout)
+            self.assertAlmostEqual(m.last_request.timeout, self.cli.timeout)
 
             m.post(
                 "%s/ga4gh/tes/v1/tasks/%s:cancel" % (
@@ -167,7 +170,7 @@ class TestHTTPClient(unittest.TestCase):
                 m.last_request.url,
                 "%s/ga4gh/tes/v1/service-info" % (self.mock_url)
             )
-            self.assertEqual(m.last_request.timeout, self.cli.timeout)
+            self.assertAlmostEqual(m.last_request.timeout, self.cli.timeout)
 
             m.get(
                 "%s/ga4gh/tes/v1/service-info" % (self.mock_url),
@@ -203,104 +206,124 @@ class TestHTTPClient(unittest.TestCase):
             )
             self.cli.wait(self.mock_id, timeout=2)
 
+    def test_request_params(self):
+
+        cli = HTTPClient(url="http://fakehost:8000", timeout=5)
+        vals = cli._request_params()
+        self.assertAlmostEqual(vals["timeout"], 5)
+        self.assertEqual(vals["headers"]["Content-type"], "application/json")
+        self.assertRaises(KeyError, lambda: vals["headers"]["Authorization"])
+        self.assertRaises(KeyError, lambda: vals["auth"])
+        self.assertRaises(KeyError, lambda: vals["data"])
+        self.assertRaises(KeyError, lambda: vals["params"])
+
+        cli = HTTPClient(url="http://fakehost:8000", user="user",
+                         password="password", token="token")
+        vals = cli._request_params(data='{"json": "string"}',
+                                   params={"query_param": "value"})
+        self.assertAlmostEqual(vals["timeout"], 10)
+        self.assertEqual(vals["headers"]["Content-type"], "application/json")
+        self.assertEqual(vals["headers"]["Authorization"], "Bearer token")
+        self.assertEqual(vals["auth"], ("user", "password"))
+        self.assertEqual(vals["data"], '{"json": "string"}')
+        self.assertEqual(vals["params"], {"query_param": "value"})
+
+    def test_append_suffixes_to_url(self):
+        urls = ["http://example.com", "http://example.com/"]
+        urls_order = ["http://example1.com", "http://example2.com"]
+        suffixes = ["foo", "/foo", "foo/", "/foo/"]
+        no_suffixes = ["", "/", "//", "///"]
+        suffixes_order = ["1", "2"]
+
+        results = append_suffixes_to_url(urls=urls, suffixes=suffixes)
+        assert len(results) == len(urls) * len(suffixes)
+        assert all(url == 'http://example.com/foo' for url in results)
+
+        results = append_suffixes_to_url(urls=urls, suffixes=no_suffixes)
+        assert len(results) == len(urls) * len(no_suffixes)
+        assert all(url == 'http://example.com' for url in results)
+
+        results = append_suffixes_to_url(urls=urls_order, suffixes=suffixes_order)
+        assert len(results) == len(urls_order) * len(suffixes_order)
+        assert results[0] == 'http://example1.com/1'
+        assert results[1] == 'http://example1.com/2'
+        assert results[2] == 'http://example2.com/1'
+        assert results[3] == 'http://example2.com/2'
+
+    def test_send_request(self):
+        mock_url = "http://example.com"
+        mock_id = "mock_id"
+        mock_urls = append_suffixes_to_url([mock_url], ["/suffix", "/"])
+
+        # invalid method
+        with pytest.raises(ValueError):
+            send_request(paths=mock_urls, method="invalid")
+
+        # errors for all paths
+        with requests_mock.Mocker() as m:
+            m.get(requests_mock.ANY, exc=requests.exceptions.ConnectTimeout)
+            with pytest.raises(requests.HTTPError):
+                send_request(paths=mock_urls)
+
+        # error on first path, 200 on second
+        with requests_mock.Mocker() as m:
+            m.get(mock_urls[0], exc=requests.exceptions.ConnectTimeout)
+            m.get(mock_urls[1], status_code=200)
+            response = send_request(paths=mock_urls)
+            assert response.status_code == 200
+            assert m.last_request.url.rstrip('/') == f"{mock_url}"
+
+        # error on first path, 404 on second
+        with requests_mock.Mocker() as m:
+            m.get(mock_urls[0], exc=requests.exceptions.ConnectTimeout)
+            m.get(mock_urls[1], status_code=404)
+            with pytest.raises(requests.HTTPError):
+                send_request(paths=mock_urls)
+
+        # 404 on first path, error on second
+        with requests_mock.Mocker() as m:
+            m.get(mock_urls[0], status_code=404)
+            m.get(mock_urls[1], exc=requests.exceptions.ConnectTimeout)
+            with pytest.raises(requests.HTTPError):
+                send_request(paths=mock_urls)
+
+        # 404 on first path, 200 on second
+        with requests_mock.Mocker() as m:
+            m.get(mock_urls[0], status_code=404)
+            m.get(mock_urls[1], status_code=200)
+            response = send_request(paths=mock_urls)
+            assert response.status_code == 200
+            assert m.last_request.url.rstrip('/') == f"{mock_url}"
+
+        # POST 200
+        with requests_mock.Mocker() as m:
+            m.post(f"{mock_url}/suffix/foo/{mock_id}:bar", status_code=200)
+            paths = append_suffixes_to_url(mock_urls, ["/foo/{id}:bar"])
+            response = send_request(paths=paths, method="post", json={},
+                                    id=mock_id)
+            assert response.status_code == 200
+            assert m.last_request.url == f"{mock_url}/suffix/foo/{mock_id}:bar"
+
+        # GET 200
+        with requests_mock.Mocker() as m:
+            m.get(f"{mock_url}/suffix/foo/{mock_id}", status_code=200)
+            paths = append_suffixes_to_url(mock_urls, ["/foo/{id}"])
+            response = send_request(paths=paths, id=mock_id)
+            assert response.status_code == 200
+            assert m.last_request.url == f"{mock_url}/suffix/foo/{mock_id}"
+
+        # POST 404
+        with requests_mock.Mocker() as m:
+            m.post(requests_mock.ANY, status_code=404, json={})
+            paths = append_suffixes_to_url(mock_urls, ["/foo"])
+            with pytest.raises(requests.HTTPError):
+                send_request(paths=paths, method="post", json={})
+            assert m.last_request.url == f"{mock_url}/foo"
 
-def test_append_suffixes_to_url():
-    urls = ["http://example.com", "http://example.com/"]
-    urls_order = ["http://example1.com", "http://example2.com"]
-    suffixes = ["foo", "/foo", "foo/", "/foo/"]
-    no_suffixes = ["", "/", "//", "///"]
-    suffixes_order = ["1", "2"]
-
-    results = append_suffixes_to_url(urls=urls, suffixes=suffixes)
-    assert len(results) == len(urls) * len(suffixes)
-    assert all(url == 'http://example.com/foo' for url in results)
-
-    results = append_suffixes_to_url(urls=urls, suffixes=no_suffixes)
-    assert len(results) == len(urls) * len(no_suffixes)
-    assert all(url == 'http://example.com' for url in results)
-
-    results = append_suffixes_to_url(urls=urls_order, suffixes=suffixes_order)
-    assert len(results) == len(urls_order) * len(suffixes_order)
-    assert results[0] == 'http://example1.com/1'
-    assert results[1] == 'http://example1.com/2'
-    assert results[2] == 'http://example2.com/1'
-    assert results[3] == 'http://example2.com/2'
-
-
-def test_send_request():
-    mock_url = "http://example.com"
-    mock_id = "mock_id"
-    mock_urls = append_suffixes_to_url([mock_url], ["/suffix", "/"])
-
-    # invalid method
-    with pytest.raises(ValueError):
-        send_request(paths=mock_urls, method="invalid")
-
-    # errors for all paths
-    with requests_mock.Mocker() as m:
-        m.get(requests_mock.ANY, exc=requests.exceptions.ConnectTimeout)
-        with pytest.raises(requests.HTTPError):
-            send_request(paths=mock_urls)
-
-    # error on first path, 200 on second
-    with requests_mock.Mocker() as m:
-        m.get(mock_urls[0], exc=requests.exceptions.ConnectTimeout)
-        m.get(mock_urls[1], status_code=200)
-        response = send_request(paths=mock_urls)
-        assert response.status_code == 200
-        assert m.last_request.url.rstrip('/') == f"{mock_url}"
-
-    # error on first path, 404 on second
-    with requests_mock.Mocker() as m:
-        m.get(mock_urls[0], exc=requests.exceptions.ConnectTimeout)
-        m.get(mock_urls[1], status_code=404)
-        with pytest.raises(requests.HTTPError):
-            send_request(paths=mock_urls)
-
-    # 404 on first path, error on second
-    with requests_mock.Mocker() as m:
-        m.get(mock_urls[0], status_code=404)
-        m.get(mock_urls[1], exc=requests.exceptions.ConnectTimeout)
-        with pytest.raises(requests.HTTPError):
-            send_request(paths=mock_urls)
-
-    # 404 on first path, 200 on second
-    with requests_mock.Mocker() as m:
-        m.get(mock_urls[0], status_code=404)
-        m.get(mock_urls[1], status_code=200)
-        response = send_request(paths=mock_urls)
-        assert response.status_code == 200
-        assert m.last_request.url.rstrip('/') == f"{mock_url}"
-
-    # POST 200
-    with requests_mock.Mocker() as m:
-        m.post(f"{mock_url}/suffix/foo/{mock_id}:bar", status_code=200)
-        paths = append_suffixes_to_url(mock_urls, ["/foo/{id}:bar"])
-        response = send_request(paths=paths, method="post", json={},
-                                id=mock_id)
-        assert response.status_code == 200
-        assert m.last_request.url == f"{mock_url}/suffix/foo/{mock_id}:bar"
-
-    # GET 200
-    with requests_mock.Mocker() as m:
-        m.get(f"{mock_url}/suffix/foo/{mock_id}", status_code=200)
-        paths = append_suffixes_to_url(mock_urls, ["/foo/{id}"])
-        response = send_request(paths=paths, id=mock_id)
-        assert response.status_code == 200
-        assert m.last_request.url == f"{mock_url}/suffix/foo/{mock_id}"
-
-    # POST 404
-    with requests_mock.Mocker() as m:
-        m.post(requests_mock.ANY, status_code=404, json={})
-        paths = append_suffixes_to_url(mock_urls, ["/foo"])
-        with pytest.raises(requests.HTTPError):
-            send_request(paths=paths, method="post", json={})
-        assert m.last_request.url == f"{mock_url}/foo"
-
-    # GET 500
-    with requests_mock.Mocker() as m:
-        m.get(f"{mock_url}/suffix/foo", status_code=500)
-        paths = append_suffixes_to_url(mock_urls, ["/foo"])
-        with pytest.raises(requests.HTTPError):
-            send_request(paths=paths)
-        assert m.last_request.url == f"{mock_url}/suffix/foo"
+        # GET 500
+        with requests_mock.Mocker() as m:
+            m.get(f"{mock_url}/suffix/foo", status_code=500)
+            paths = append_suffixes_to_url(mock_urls, ["/foo"])
+            with pytest.raises(requests.HTTPError):
+                send_request(paths=paths)
+            assert m.last_request.url == f"{mock_url}/suffix/foo"
diff --git a/tests/test_models.py b/tests/test_models.py
index 2c8dd95..c1cebd7 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -1,67 +1,250 @@
 import json
 import unittest
 
-from tes.models import Task, Executor, Input, Output, strconv
+from copy import deepcopy
 
+from tes.models import (
+    Executor,
+    ExecutorLog,
+    Input,
+    Output,
+    OutputFileLog,
+    Resources,
+    Task,
+    TaskLog,
+    datetime_json_handler,
+    int64conv,
+    list_of,
+    strconv,
+    timestampconv,
+    _drop_none,
+)
 
-class TestModels(unittest.TestCase):
-    task = Task(
-        executors=[
-            Executor(
-                image="alpine",
-                command=["echo", "hello"]
-            )
-        ]
-    )
-
-    expected = {
-        "executors": [
-            {
-                "image": "alpine",
-                "command": ["echo", "hello"]
-            }
-        ]
-    }
 
-    def test_strconv(self):
-        self.assertTrue(strconv("foo"), u"foo")
-        self.assertTrue(strconv(["foo", "bar"]), [u"foo", u"bar"])
-        self.assertTrue(strconv(("foo", "bar")), (u"foo", u"bar"))
-        self.assertTrue(strconv(1), 1)
+task_valid = Task(
+    executors=[
+        Executor(
+            image="alpine",
+            command=["echo", "hello"]
+        )
+    ]
+)
+
+
+datetm = "2018-01-01T00:00:00Z"
+task_valid_full = Task(
+    id="foo",
+    state="COMPLETE",
+    name="some_task",
+    description="some description",
+    resources=Resources(
+        cpu_cores=1,
+        ram_gb=2,
+        disk_gb=3,
+        preemptible=True,
+        zones=["us-east-1", "us-west-1"],
+    ),
+    executors=[
+        Executor(
+            image="alpine",
+            command=["echo", "hello"],
+            workdir="/abs/path",
+            stdin="/abs/path",
+            stdout="/abs/path",
+            stderr="/abs/path",
+            env={"VAR": "value"}
+        ),
+        Executor(
+            image="alpine",
+            command=["echo", "worls"]
+        )
+    ],
+    inputs=[
+        Input(
+            url="s3:/some/path",
+            path="/abs/path"
+        ),
+        Input(
+            content="foo",
+            path="/abs/path"
+        )
+    ],
+    outputs=[
+        Output(
+            url="s3:/some/path",
+            path="/abs/path"
+        )
+    ],
+    volumes=[],
+    tags={"key": "value", "key2": "value2"},
+    logs=[
+        TaskLog(
+            start_time=datetm,  # type: ignore
+            end_time=datetm,  # type: ignore
+            metadata={"key": "value", "key2": "value2"},
+            logs=[
+                ExecutorLog(
+                    start_time=datetm,  # type: ignore
+                    end_time=datetm,  # type: ignore
+                    exit_code=0,
+                    stdout="hello",
+                    stderr="world"
+                )
+            ],
+            outputs=[
+                OutputFileLog(
+                    url="s3:/some/path",
+                    path="/abs/path",
+                    size_bytes=int64conv(123)  # type: ignore
+                )
+            ],
+            system_logs=[
+                "some system log message",
+                "some other system log message"
+            ]
+        )
+    ],
+    creation_time=datetm  # type: ignore
+)
 
+task_invalid = Task(
+    executors=[
+        Executor(  # type: ignore
+            image="alpine",
+            command=["echo", "hello"],
+            stdin="relative/path",
+            stdout="relative/path",
+            stderr="relative/path",
+            env={1: 2}
+        )
+    ],
+    inputs=[
+        Input(
+            url="s3:/some/path",
+            content="foo"
+        ),
+        Input(
+            path="relative/path"
+        )
+    ],
+    outputs=[
+        Output(),
+        Output(
+            url="s3:/some/path",
+            path="relative/path"
+        )
+    ],
+    volumes=['/abs/path', 'relative/path'],
+    tags={1: 2}
+)
+
+expected = {
+    "executors": [
+        {
+            "image": "alpine",
+            "command": ["echo", "hello"]
+        }
+    ]
+}
+
+
+class TestModels(unittest.TestCase):
+
+    def test_list_of(self):
+        validator = list_of(str)
+        self.assertEqual(list_of(str), validator)
+        self.assertEqual(
+            repr(validator),
+            "<instance_of validator for type <class 'str'>>"
+        )
         with self.assertRaises(TypeError):
             Input(
-                url="s3:/some/path", path="/opt/foo", content=123
+                url="s3:/some/path",
+                path="/opt/foo",
+                content=123  # type: ignore
             )
-
-    def test_list_of(self):
         with self.assertRaises(TypeError):
             Task(
                 inputs=[
                     Input(
                         url="s3:/some/path", path="/opt/foo"
                     ),
-                    "foo"
+                    "foo"  # type: ignore
                 ]
             )
 
+    def test_drop_none(self):
+        self.assertEqual(_drop_none({}), {})
+        self.assertEqual(_drop_none({"foo": None}), {})
+        self.assertEqual(_drop_none({"foo": 1}), {"foo": 1})
+        self.assertEqual(_drop_none({"foo": None, "bar": 1}), {"bar": 1})
+        self.assertEqual(_drop_none({"foo": [1, None, 2]}), {"foo": [1, 2]})
+        self.assertEqual(_drop_none({"foo": {"bar": None}}), {"foo": {}})
+        self.assertEqual(
+            _drop_none({"foo": {"bar": None}, "baz": 1}),
+            {"foo": {}, "baz": 1}
+        )
+
+    def test_strconv(self):
+        self.assertTrue(strconv("foo"), u"foo")
+        self.assertTrue(strconv(["foo", "bar"]), [u"foo", u"bar"])
+        self.assertTrue(strconv(("foo", "bar")), (u"foo", u"bar"))
+        self.assertTrue(strconv(1), 1)
+        self.assertTrue(strconv([1]), [1])
+
+    def test_int64conv(self):
+        self.assertEqual(int64conv("1"), 1)
+        self.assertEqual(int64conv("-1"), -1)
+        self.assertIsNone(int64conv(None))
+
+    def test_timestampconv(self):
+        tm = timestampconv("2018-02-01T00:00:00Z")
+        self.assertIsNotNone(tm)
+        assert tm is not None
+        self.assertAlmostEqual(tm.year, 2018)
+        self.assertAlmostEqual(tm.month, 2)
+        self.assertAlmostEqual(tm.day, 1)
+        self.assertAlmostEqual(tm.hour, 0)
+        self.assertAlmostEqual(tm.timestamp(), 1517443200.0)
+        self.assertIsNone(timestampconv(None))
+
+    def test_datetime_json_handler(self):
+        tm = timestampconv("2018-02-01T00:00:00Z")
+        tm_iso = '2018-02-01T00:00:00+00:00'
+        assert tm is not None
+        self.assertEqual(datetime_json_handler(tm), tm_iso)
+        with self.assertRaises(TypeError):
+            datetime_json_handler(None)
+        with self.assertRaises(TypeError):
+            datetime_json_handler("abc")
+        with self.assertRaises(TypeError):
+            datetime_json_handler(2001)
+        with self.assertRaises(TypeError):
+            datetime_json_handler(tm_iso)
+
     def test_as_dict(self):
-        self.assertEqual(self.task.as_dict(), self.expected)
+        task = deepcopy(task_valid)
+        self.assertEqual(task.as_dict(), expected)
+        with self.assertRaises(KeyError):
+            task.as_dict()['inputs']
+        self.assertIsNone(task.as_dict(drop_empty=False)['inputs'])
 
     def test_as_json(self):
-        self.assertEqual(self.task.as_json(), json.dumps(self.expected))
+        task = deepcopy(task_valid)
+        self.assertEqual(task.as_json(), json.dumps(expected))
 
     def test_is_valid(self):
-        self.assertTrue(self.task.is_valid()[0])
+        task = deepcopy(task_valid)
+        self.assertTrue(task.is_valid()[0])
 
-        task2 = self.task
-        task2.inputs = [Input(path="/opt/foo")]
-        self.assertFalse(task2.is_valid()[0])
+        task = deepcopy(task_valid_full)
+        self.assertTrue(task.is_valid()[0])
 
-        task3 = self.task
-        task3.outputs = [
-            Output(
-                url="s3:/some/path", path="foo"
-            )
-        ]
-        self.assertFalse(task3.is_valid()[0])
+        task = deepcopy(task_invalid)
+        task.executors[0].image = None  # type: ignore
+        task.executors[0].command = None  # type: ignore
+        self.assertFalse(task.is_valid()[0])
+
+        task = deepcopy(task_invalid)
+        task.executors = None
+        self.assertFalse(task.is_valid()[0])
diff --git a/tests/test_utils.py b/tests/test_utils.py
index c07dd09..b7fe5ed 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -5,7 +5,23 @@ import json
 import unittest
 
 from tes.utils import camel_to_snake, unmarshal, UnmarshalError
-from tes.models import Input, Task, CreateTaskResponse
+from tes.models import (
+    CancelTaskRequest,
+    CancelTaskResponse,
+    CreateTaskResponse,
+    Executor,
+    ExecutorLog,
+    GetTaskRequest,
+    Input,
+    ListTasksRequest,
+    ListTasksResponse,
+    Output,
+    OutputFileLog,
+    Resources,
+    ServiceInfo,
+    Task,
+    TaskLog,
+)
 
 
 class TestUtils(unittest.TestCase):
@@ -19,7 +35,110 @@ class TestUtils(unittest.TestCase):
         self.assertEqual(camel_to_snake(case3), "foo_bar")
 
     def test_unmarshal(self):
-        test_invalid_dict = {"adfasd": "bar"}
+
+        # test unmarshalling with no or minimal contents
+        try:
+            unmarshal(
+                CancelTaskRequest(id="foo").as_json(),
+                CancelTaskRequest
+            )
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(CancelTaskResponse().as_json(), CancelTaskResponse)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(
+                CreateTaskResponse(id="foo").as_json(),
+                CreateTaskResponse
+            )
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(Executor(
+                image="alpine", command=["echo", "hello"]).as_json(),
+                Executor
+            )
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(ExecutorLog().as_json(), ExecutorLog)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(
+                GetTaskRequest(id="foo", view="BASIC").as_json(),
+                GetTaskRequest
+            )
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(Input().as_json(), Input)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(ListTasksRequest().as_json(), ListTasksRequest)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(ListTasksResponse().as_json(), ListTasksResponse)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(Output().as_json(), Output)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(OutputFileLog().as_json(), OutputFileLog)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(Resources().as_json(), Resources)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(ServiceInfo().as_json(), ServiceInfo)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(Task().as_json(), Task)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        try:
+            unmarshal(TaskLog().as_json(), TaskLog)
+        except Exception:
+            self.fail("Raised ExceptionType unexpectedly!")
+
+        # test special cases
+        self.assertIsNone(unmarshal(None, Input))
+        with self.assertRaises(TypeError):
+            unmarshal([], Input)
+        with self.assertRaises(TypeError):
+            unmarshal(1, Input)
+        with self.assertRaises(TypeError):
+            unmarshal(1.3, Input)
+        with self.assertRaises(TypeError):
+            unmarshal(True, Input)
+        with self.assertRaises(TypeError):
+            unmarshal('foo', Input)
+
+        # test with some interesting contents
+        test_invalid_dict = {"foo": "bar"}
         test_invalid_str = json.dumps(test_invalid_dict)
         with self.assertRaises(UnmarshalError):
             unmarshal(test_invalid_dict, CreateTaskResponse)
@@ -33,7 +152,7 @@ class TestUtils(unittest.TestCase):
         }
         test_simple_str = json.dumps(test_simple_dict)
         o1 = unmarshal(test_simple_dict, Input)
-        o2 = unmarshal(test_simple_str, Input)
+        o2 = unmarshal(test_simple_str, Input, convert_camel_case=False)
         self.assertTrue(isinstance(o1, Input))
         self.assertTrue(isinstance(o2, Input))
         self.assertEqual(o1, o2)
@@ -92,6 +211,13 @@ class TestUtils(unittest.TestCase):
                     ]
                 }
             ],
+            "resources": {
+                "cpu_cores": 1,
+                "ram_gb": 2,
+                "disk_gb": 3,
+                "preemptible": True,
+                "zones": ["us-east-1", "us-west-1"]
+            },
             "creation_time": "2017-10-09T17:00:00.0Z"
         }
 
@@ -100,7 +226,7 @@ class TestUtils(unittest.TestCase):
         o2 = unmarshal(test_complex_str, Task)
         self.assertTrue(isinstance(o1, Task))
         self.assertTrue(isinstance(o2, Task))
-        self.assertEqual(o1, o2)
+        self.assertAlmostEqual(o1, o2)
         expected = test_complex_dict.copy()
 
         # handle expected conversions
@@ -122,7 +248,6 @@ class TestUtils(unittest.TestCase):
         expected["creation_time"] = dateutil.parser.parse(
             expected["creation_time"]
         )
-
         self.assertEqual(o1.as_dict(), expected)
 
     def test_unmarshal_types(self):

Increase unit test code coverage
According to the most recent code coverage report (on branch [`api-location`](https://github.com/ohsu-comp-bio/py-tes/tree/api-location) in PR #46), there is still a bit of untested code:

```console
Name              Stmts   Miss  Cover   Missing
-----------------------------------------------
tes/__init__.py       5      0   100%
tes/client.py       111      4    96%   133, 186-187, 211
tes/models.py       202     29    86%   29, 53, 65, 77, 87, 292, 296, 298, 300-301, 303-304, 306-307, 309-311, 320, 322, 324, 329, 331, 336-339, 342-344
tes/utils.py         57     11    81%   34-37, 44, 72, 81-86
-----------------------------------------------
TOTAL               375     44    88%
```

Increase code coverage by providing unit tests for the missing statements in:

- [ ] `tes/client.py`
- [ ] `tes/models.py`
- [ ] `tes/utils.py`
tests/test_utils.py::TestUtils::test_unmarshal tests/test_client.py::TestHTTPClient::test_request_params tests/test_models.py::TestModels::test_is_valid tests/test_models.py::TestModels::test_list_of
tests/test_utils.py::TestUtils::test_unmarshal_types tests/test_utils.py::TestUtils::test_camel_to_snake tests/test_client.py::TestHTTPClient::test_send_request tests/test_client.py::TestHTTPClient::test_create_task tests/test_client.py::TestHTTPClient::test_list_tasks tests/test_client.py::TestHTTPClient::test_get_service_info tests/test_client.py::TestHTTPClient::test_get_task tests/test_client.py::TestHTTPClient::test_wait tests/test_client.py::TestHTTPClient::test_cancel_task tests/test_client.py::TestHTTPClient::test_cli tests/test_client.py::TestHTTPClient::test_append_suffixes_to_url tests/test_models.py::TestModels::test_int64conv tests/test_models.py::TestModels::test_strconv tests/test_models.py::TestModels::test_datetime_json_handler tests/test_models.py::TestModels::test_timestampconv tests/test_models.py::TestModels::test_as_dict tests/test_models.py::TestModels::test_drop_none tests/test_models.py::TestModels::test_as_json