diff --git a/dpctl/_sycl_event.pyx b/dpctl/_sycl_event.pyx
index a6b909427c..f78e19c326 100644
--- a/dpctl/_sycl_event.pyx
+++ b/dpctl/_sycl_event.pyx
@@ -88,8 +88,10 @@ cdef class _SyclEvent:
     """
 
     def __dealloc__(self):
-        DPCTLEvent_Wait(self._event_ref)
-        DPCTLEvent_Delete(self._event_ref)
+        if (self._event_ref):
+            DPCTLEvent_Wait(self._event_ref)
+            DPCTLEvent_Delete(self._event_ref)
+        self._event_ref = NULL
         self.args = None
 
 
diff --git a/dpctl/tests/_helper.py b/dpctl/tests/_helper.py
index cea9d3d450..aafa845130 100644
--- a/dpctl/tests/_helper.py
+++ b/dpctl/tests/_helper.py
@@ -11,3 +11,15 @@ def has_cpu(backend="opencl"):
 
 def has_sycl_platforms():
     return bool(len(dpctl.get_platforms()))
+
+
+def create_invalid_capsule():
+    """Creates an invalid capsule for the purpose of testing dpctl
+    constructors that accept capsules.
+    """
+    import ctypes
+
+    ctor = ctypes.pythonapi.PyCapsule_New
+    ctor.restype = ctypes.py_object
+    ctor.argtypes = [ctypes.c_void_p, ctypes.c_char_p, ctypes.c_void_p]
+    return ctor(id(ctor), b"invalid", 0)
diff --git a/dpctl/tests/test_sycl_context.py b/dpctl/tests/test_sycl_context.py
index c938caf074..9d09a6117c 100644
--- a/dpctl/tests/test_sycl_context.py
+++ b/dpctl/tests/test_sycl_context.py
@@ -14,13 +14,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-""" Defines unit test cases for the SyclContxt class.
+""" Defines unit test cases for the :class:`dpctl.SyclContext` class.
 """
 
 import pytest
 
 import dpctl
 
+from ._helper import create_invalid_capsule
+
 list_of_valid_filter_selectors = [
     "opencl",
     "opencl:gpu",
@@ -210,3 +212,16 @@ def test_cpython_api():
     r2 = ctx.addressof_ref()
     r1 = get_context_ref_fn(ctx)
     assert r1 == r2
+
+
+def test_invalid_capsule():
+    cap = create_invalid_capsule()
+    with pytest.raises(ValueError):
+        dpctl.SyclContext(cap)
+
+
+def test_multi_device_different_platforms():
+    devs = dpctl.get_devices()  # all devices
+    if len(devs) > 1:
+        with pytest.raises(ValueError):
+            dpctl.SyclContext(devs)
diff --git a/dpctl/tests/test_sycl_event.py b/dpctl/tests/test_sycl_event.py
index 62b93dc95d..4e76534bd8 100644
--- a/dpctl/tests/test_sycl_event.py
+++ b/dpctl/tests/test_sycl_event.py
@@ -25,7 +25,7 @@
 import dpctl.program as dpctl_prog
 from dpctl import event_status_type as esty
 
-from ._helper import has_cpu
+from ._helper import create_invalid_capsule, has_cpu
 
 
 def produce_event(profiling=False):
@@ -223,6 +223,12 @@ def test_event_capsule():
     del cap2
 
 
+def test_event_invalid_capsule():
+    cap = create_invalid_capsule()
+    with pytest.raises(TypeError):
+        dpctl.SyclEvent(cap)
+
+
 def test_addressof_ref():
     ev = dpctl.SyclEvent()
     ref = ev.addressof_ref()
diff --git a/dpctl/tests/test_sycl_queue.py b/dpctl/tests/test_sycl_queue.py
index 5b978153ae..8c31dcc8b0 100644
--- a/dpctl/tests/test_sycl_queue.py
+++ b/dpctl/tests/test_sycl_queue.py
@@ -21,6 +21,8 @@
 
 import dpctl
 
+from ._helper import create_invalid_capsule
+
 list_of_standard_selectors = [
     dpctl.select_accelerator_device,
     dpctl.select_cpu_device,
@@ -359,6 +361,8 @@ def test_context_not_equals():
     ctx_cpu = cpuQ.get_sycl_context()
     assert ctx_cpu != ctx_gpu
     assert hash(ctx_cpu) != hash(ctx_gpu)
+    assert gpuQ != cpuQ
+    assert hash(cpuQ) != hash(gpuQ)
 
 
 def test_context_equals():
@@ -497,11 +501,34 @@ def test_constructor_many_arg():
         dpctl.SyclQueue(ctx)
 
 
+def test_constructor_inconsistent_ctx_dev():
+    try:
+        q = dpctl.SyclQueue("cpu")
+    except dpctl.SyclQueueCreationError:
+        pytest.skip("Failed to create CPU queue")
+    cpuD = q.sycl_device
+    n_eu = cpuD.max_compute_units
+    n_half = n_eu // 2
+    try:
+        d0, d1 = cpuD.create_sub_devices(partition=[n_half, n_eu - n_half])
+    except Exception:
+        pytest.skip("Could not create CPU sub-devices")
+    ctx = dpctl.SyclContext(d0)
+    with pytest.raises(dpctl.SyclQueueCreationError):
+        dpctl.SyclQueue(ctx, d1)
+
+
+def test_constructor_invalid_capsule():
+    cap = create_invalid_capsule()
+    with pytest.raises(TypeError):
+        dpctl.SyclQueue(cap)
+
+
 def test_queue_wait():
     try:
         q = dpctl.SyclQueue()
     except dpctl.SyclQueueCreationError:
-        pytest.skip("Failed to create device with supported filter")
+        pytest.skip("Failed to create default queue")
     q.wait()