Rust polars Series::series_equal method asserts even if incorrect

Question

My test asserts true, even though I have different values in the Series.

In the below test index 0 (100.94947) is wrong but it passes

pub fn convert_tb_to_tib(s: Series) -> Series {
    let result = s.cast(&DataType::Float64).unwrap() * 0.90949470177293;
    result
}


    fn test_convert_tb_to_tib() {
        let test_s = Series::new("", &[100, 200, 300, 400]);
        let transformed_s = convert_tb_to_tib(test_s);
        let expected_s = Series::new("", &[100.94947, 181.89894, 272.848411, 373.797881]);
        transformed_s.series_equal(&expected_s);
    }

test wrangle::tests::test_convert_tb_to_tib ... ok

I can evidence this by using the assert_eq! macro instead:

    fn test_convert_tb_to_tib() {
        let test_s = Series::new("", &[100, 200, 300, 400]);
        let transformed_s = convert_tb_to_tib(test_s);
        let expected_s = Series::new("", &[100.94947, 181.89894, 272.848411, 373.797881]);
        assert_eq!(transformed_s, expected_s);
    }

thread 'wrangle::tests::test_convert_tb_to_tib' panicked at 'assertion failed: `(left == right)`
  left: `shape: (4,)
Series: '' [f64]
[
        90.94947
        181.89894
        272.848411
        363.797881
]`,
 right: `shape: (4,)
Series: '' [f64]
[
        100.94947
        181.89894
        272.848411
        373.797881
]`', src/wrangle.rs:108:9

Why does this test pass when using the series_eq method?

Answer 1

series_equal() doesn't assert anything, it only compares and returns a boolean.

You need to assert!() its result:

assert!(transformed_s.series_equal(&expected_s));

But I recommend you to just use assert_eq!().