> ## Documentation Index
> Fetch the complete documentation index at: https://demo.agenticlabs.com/llms.txt
> Use this file to discover all available pages before exploring further.

# snj_solver_test.py

Here's a detailed explanation of the `test/solver_tests/snj_solver_test.py` file:

## High-level description

This file contains unit tests for the SpectralNeighborJoiningSolver in Cassiopeia's solver module. It tests various aspects of the solver, including its constructor, core functionality, and integration with different types of phylogenetic trees.

## Code Structure

The main class `TestSpectralNeighborJoiningSolver` inherits from `unittest.TestCase` and contains multiple test methods. The `setUp` method initializes common test data and objects used across different tests. Helper functions like `find_triplet_structure` and `assertTripletCorrectness` are defined outside the class to assist in verifying tree structures.

## Symbols

### TestSpectralNeighborJoiningSolver

#### Description

This is the main test class that contains all the unit tests for the SpectralNeighborJoiningSolver.

#### Internal Logic

1. Initializes test data in the `setUp` method.
2. Defines various test methods to check different aspects of the solver.
3. Uses helper functions to verify tree structures.

### find\_triplet\_structure

#### Description

A helper function that identifies the two nodes with the most similar ancestry in a triplet of nodes.

#### Inputs

| Name    | Type             | Description                   |
| :------ | :--------------- | :---------------------------- |
| triplet | tuple            | A tuple of three node names   |
| T       | networkx.DiGraph | The tree containing the nodes |

#### Outputs

| Name      | Type | Description                                             |
| :-------- | :--- | :------------------------------------------------------ |
| structure | str  | The structure of the triplet ("ab", "ac", "bc", or "-") |

### assertTripletCorrectness

#### Description

A helper method to check if two trees are isomorphic by comparing their triplet structures.

#### Inputs

| Name           | Type             | Description                             |
| :------------- | :--------------- | :-------------------------------------- |
| self           | TestCase         | The test case instance                  |
| nodes          | List\[str]       | List of leaf nodes to get triplets from |
| expected\_tree | networkx.DiGraph | The expected tree structure             |
| observed\_tree | networkx.DiGraph | The observed tree structure             |

## Test Methods

### test\_constructor

Tests the constructor of the SpectralNeighborJoiningSolver and checks for proper initialization and error handling.

### test\_compute\_svd2\_pairwise

Tests the `_compute_svd2` method for pairwise comparisons of subsets.

### test\_compute\_svd2\_N3

Tests the `_compute_svd2` method when there are only 3 subsets left.

### test\_update\_dissimilarity\_map\_base

Tests the `update_dissimilarity_map` method for updating the lambda matrix.

### test\_update\_dissimilarity\_map\_N3

Tests the `update_dissimilarity_map` method when there are only 3 subsets left.

### test\_get\_dissimilarity\_map

Tests the `get_dissimilarity_map` method for outputting a lambda matrix.

### test\_find\_cherry

Tests the `find_cherry` method for identifying the closest pair of nodes.

### test\_basic\_solver

Tests the basic functionality of the solver on a root-specified input tree.

### test\_snj\_solver\_weights

Tests the solver with a perfect phylogenetic tree and priors.

### test\_pp\_solver

Integration test for a Perfect Phylogenetic tree.

### test\_duplicate\_sample

Tests the solving of a tree with duplicate leaves.

### test\_integration1

Integration test on a 7-leaf tree.

### test\_integration2

Integration test on a 10-leaf tree.

### test\_setup\_root\_finder\_missing\_dissimilarity\_map

Checks that the root is still set despite missing dissimilarity map.

### test\_setup\_root\_finder\_existing\_dissimilarity\_map

Checks that the root is still set with an existing dissimilarity map.

## Dependencies

The test file imports and uses several modules and classes:

* Standard Python libraries: typing, itertools, unittest, mock
* Third-party libraries: networkx, numpy, pandas
* Cassiopeia modules: cassiopeia as cas

## Error Handling

The tests use various assertions to check for expected behavior and raise exceptions when unexpected results occur.

This test suite provides comprehensive coverage of the SpectralNeighborJoiningSolver's functionality, ensuring its correctness and robustness across different scenarios and tree structures.