Add automated test

tests/test_laser_energy.py

@@ -0,0 +1,57 @@
+"""
+This test file is part of the openPMD-viewer.
+
+It checks that the function `get_electromagnetic_energy` works correctly
+
+Usage:
+This file is meant to be run from the root directory of openPMD-viewer,
+by any of the following commands
+$ python tests/test_laser_energy.py
+$ py.test
+$ python -m pytest tests
+
+Copyright 2024, openPMD-viewer contributors
+Authors: Remi Lehe
+License: 3-Clause-BSD-LBNL
+"""
+from openpmd_viewer.addons import LpaDiagnostics
+from scipy.constants import c
+import numpy as np
+
+# Download required datasets
+import os
+def download_if_absent( dataset_name ):
+    "Function that downloads and decompress a chosen dataset"
+    if os.path.exists( dataset_name ) is False:
+        import wget, tarfile
+        tar_name = "%s.tar.gz" %dataset_name
+        url = "https://github.com/openPMD/openPMD-example-datasets/raw/draft/%s" %tar_name
+        wget.download(url, tar_name)
+        with tarfile.open( tar_name ) as tar_file:
+            tar_file.extractall()
+        os.remove( tar_name )
+download_if_absent( 'example-thetaMode' )
+
+def test_laser_energy():
+    """
+    Check that the function `get_electromagnetic_energy` gives the same result
+    as the engineering formula for a Gaussian pulse
+
+    E = 2.7e-5*(a0*w0/lambd)**2*(tau[fs])
+    """
+    ts = LpaDiagnostics('./example-thetaMode/hdf5')
+    iteration = 300
+
+    # Evaluate the laser energy using the engineering formula
+    a0 = ts.get_a0(iteration=iteration, pol='y')
+    w0 = ts.get_laser_waist(iteration=iteration, pol='y')
+    tau_fs = ts.get_ctau(iteration=iteration, pol='y') / c * 1e15
+    omega = ts.get_main_frequency(iteration=iteration, pol='y')
+    lambd = 2*np.pi*c/omega
+    E_eng = 2.7e-5*(a0*w0/lambd)**2*tau_fs
+
+    # Evaluate the laser energy using the function
+    E_func = ts.get_electromagnetic_energy(iteration=iteration)
+
+    # Compare the two results
+    assert np.isclose(E_eng, E_func, rtol=0.04)