Failing Test Pair - Find First Conflicting Test Case

Question

## Problem

You are given a list of test results, each as a tuple `(input_val, expected_output, actual_output)`. A test "fails" when `expected_output != actual_output`.

A "failing pair" is defined as two consecutive tests (by index) where both fail AND they share the same `input_val`. Return the index of the first such pair `(i, i+1)`, or `-1` if none exists.

```python
def first_failing_pair(
    results: list[tuple[int, int, int]]
) -> int:
```

## Example

```
results = [
  (5, 10, 10),  # pass
  (3, 6,  7),   # fail
  (3, 6,  8),   # fail, same input as prev -> pair at index 1
  (7, 14, 14),
]
Output: 1

results = [(1,2,3),(2,4,5),(2,4,5)]
# index 1 and 2 both fail and share input 2 -> Output: 1
```

## Follow-ups

1. Extend to find ALL failing pairs, not just the first.
2. What if "failing pair" means any two failing tests within a window of size `w` (not just consecutive)?
3. How would you adapt this to a streaming input where results arrive one at a time?
4. Group all failing tests by `input_val` and return the `input_val` with the most failures.

Failing Test Pair - Find First Conflicting Test Case

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