docstr: Tests the default parameters.
docstr_tok: ["Tests","the","default","parameters","."]
code: def test_default_construction_1d(self):
      """Tests the default parameters."""
      process = BrownianMotion()
      self.assertEqual(process.dim(), 1)
      drift_fn = process.drift_fn()
      # Drift should be zero.
      t0 = np.array([0.2, 0.7, 0.9])
      t1 = t0 + [0.1, 0.8, 0.3]
      drifts = self.evaluate(drift_fn(t0, None))
      total_drift_fn = process.total_drift_fn()
      self.assertAlmostEqual(
          self.evaluate(total_drift_fn(0.4, 0.5)), 0.0, places=7
      )
      self.assertArrayNear(drifts, np.zeros([3]), 1e-10)
      variances = self.evaluate(process.total_covariance_fn()(t0, t1))
      self.assertArrayNear(variances, t1 - t0, 1e-10)
      self.assertAlmostEqual(
          self.evaluate(process.total_covariance_fn()(0.41, 0.55)),
          0.14,
          places=7,
      )
  
file_path: tf-quant-finance/tf_quant_finance/models/legacy/brownian_motion_test.py
imports: import numpy
  import tensorflow.compat.v2
  from tensorflow.python.framework import test_util
  from tf_quant_finance.models.legacy.brownian_motion import BrownianMotion
label_desc: Use image node_id 2 for calling the BrownianMotionTest obj's underlying member method code with example usage: obj.test_default_construction_1d() without return types