add tests for added util functions

mitiq/shadows/test/test_shadows_utils.py

@@ -3,13 +3,18 @@
 # This source code is licensed under the GPL license (v3) found in the
 # LICENSE file in the root directory of this source tree.
 
-"""Defines utility functions for classical shadows protocol."""
+import math
+
+import numpy as np
 
 import mitiq
 from mitiq.shadows.shadows_utils import (
+    batch_calibration_data,
     create_string,
+    fidelity,
     n_measurements_opts_expectation_bound,
     n_measurements_tomography_bound,
+    valid_bitstrings,
 )
 
 
@@ -19,16 +24,33 @@ def test_create_string():
     assert create_string(str_len, loc_list) == "01010"
 
 
+def test_valid_bitstrings():
+    num_qubits = 5
+    bitstrings_on_5_qubits = valid_bitstrings(num_qubits)
+    assert len(bitstrings_on_5_qubits) == 2**num_qubits
+    assert all(b == "0" or b == "1" for b in bitstrings_on_5_qubits.pop())
+
+    num_qubits = 4
+    max_hamming_weight = 2
+    bitstrings_on_3_qubits_hamming_2 = valid_bitstrings(
+        num_qubits, max_hamming_weight
+    )
+    assert len(bitstrings_on_3_qubits_hamming_2) == sum(
+        math.comb(num_qubits, i) for i in range(max_hamming_weight + 1)
+    )  # sum_{i == 0}^{max_hamming_weight} (num_qubits choose i)
+
+
+def test_batch_calibration_data():
+    data = (["010", "110", "000", "001"], ["XXY", "ZYY", "ZZZ", "XYZ"])
+    num_batches = 2
+    for bits, paulis in batch_calibration_data(data, num_batches):
+        assert len(bits) == len(paulis) == num_batches
+
+
 def test_n_measurements_tomography_bound():
-    assert (
-        n_measurements_tomography_bound(0.5, 2) == 2176
-    ), f"Expected 2176, got {n_measurements_tomography_bound(0.5, 2)}"
-    assert (
-        n_measurements_tomography_bound(1.0, 1) == 136
-    ), f"Expected 136, got {n_measurements_tomography_bound(1.0, 1)}"
-    assert (
-        n_measurements_tomography_bound(0.1, 3) == 217599
-    ), f"Expected 217599, got {n_measurements_tomography_bound(0.1, 3)}"
+    assert n_measurements_tomography_bound(0.5, 2) == 2176
+    assert n_measurements_tomography_bound(1.0, 1) == 136
+    assert n_measurements_tomography_bound(0.1, 3) == 217599
 
 
 def test_n_measurements_opts_expectation_bound():
@@ -38,5 +60,13 @@ def test_n_measurements_opts_expectation_bound():
         mitiq.PauliString("Z"),
     ]
     N, K = n_measurements_opts_expectation_bound(0.5, observables, 0.1)
-    assert isinstance(N, int), f"Expected int, got {type(N)}"
-    assert isinstance(K, int), f"Expected int, got {type(K)}"
+    assert isinstance(N, int)
+    assert isinstance(K, int)
+
+
+def test_fidelity():
+    state_vector = np.array([0.5, 0.5, 0.5, 0.5])
+    rho = np.eye(4) / 4
+    assert np.isclose(
+        fidelity(state_vector, rho), 0.25
+    ), f"Expected 0.25, got {fidelity(state_vector, rho)}"