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# simple_fit_subclone_simulator_test.py

## High-level description

This file contains unit tests for the SimpleFitSubcloneSimulator class, which simulates a clonal population that develops one fit subclone. The tests verify the correctness of the simulated phylogenetic tree structure and branch lengths in both deterministic and stochastic scenarios.

## Symbols

### TestSimpleFitSubcloneSimulator

#### Description

A unittest.TestCase subclass that contains test methods for the SimpleFitSubcloneSimulator class.

### test\_deterministic

#### Description

Tests the SimpleFitSubcloneSimulator with deterministic branch lengths to ensure the generated phylogeny is correct.

#### Internal Logic

1. Creates a SimpleFitSubcloneSimulator instance with specific parameters.
2. Simulates a tree using the simulator.
3. Asserts that the generated tree has the expected structure:
   * Correct node names
   * Correct edge connections
   * Correct node times

### test\_stochastic

#### Description

Tests the SimpleFitSubcloneSimulator with stochastic branch lengths to ensure non-deterministic behavior.

#### Internal Logic

1. Sets a random seed for reproducibility.
2. Defines two functions for generating random branch lengths:
   * `branch_length_neutral`: Returns an exponentially distributed value with mean 1.0
   * `branch_length_fit`: Returns an exponentially distributed value with mean 0.5
3. Creates a SimpleFitSubcloneSimulator instance with the random branch length functions.
4. Simulates a tree using the simulator.
5. Extracts branch lengths for non-leaf nodes.
6. Asserts that all branch lengths are distinct, confirming non-determinism.

## Dependencies

| Dependency                                      | Purpose                                                |
| :---------------------------------------------- | :----------------------------------------------------- |
| numpy                                           | Used for random number generation and array operations |
| unittest                                        | Provides the testing framework                         |
| cassiopeia.simulator.SimpleFitSubcloneSimulator | The class being tested                                 |

## Notes

* The tests cover both deterministic and stochastic scenarios, ensuring the simulator works correctly in different conditions.
* The stochastic test uses a fixed random seed to ensure reproducibility while still testing random behavior.
* The tests focus on verifying the tree structure, node naming, and branch length generation, which are key aspects of the SimpleFitSubcloneSimulator's functionality.