use crate::validators::{ValidationReport, ValidationResult, Validator};
use polars::prelude::*;
pub struct MeanBetweenValidator {
pub min: f64,
pub max: f64,
}
impl Validator for MeanBetweenValidator {
fn name(&self) -> &'static str {
"MeanBetween"
}
fn validate(&self, df: &DataFrame, column_name: &str) -> ValidationResult<ValidationReport> {
let series = df.column(column_name)?;
let f64_series = match series.strict_cast(&DataType::Float64) {
Ok(s) => s,
Err(_) => {
return Ok(ValidationReport {
status: "skipped",
details: Some("column could not be cast to a numeric type".to_string()),
});
}
};
let values = f64_series.f64()?;
if let Some(mean) = values.mean() {
if mean >= self.min && mean <= self.max {
Ok(ValidationReport {
status: "pass",
details: None,
})
} else {
Ok(ValidationReport {
status: "fail",
details: Some(format!(
"observed_mean={:.2}, min={}, max={}",
mean, self.min, self.max
)),
})
}
} else {
Ok(ValidationReport {
status: "skipped",
details: Some("column contains no non-null values".to_string()),
})
}
}
}
#[cfg(test)]
mod tests {
use super::*;
fn make_f64_df(values: &[Option<f64>]) -> DataFrame {
let s = Series::new("col".into(), values.to_vec());
DataFrame::new(vec![s.into()]).unwrap()
}
fn make_str_df(values: &[Option<&str>]) -> DataFrame {
let s = Series::new("col".into(), values.to_vec());
DataFrame::new(vec![s.into()]).unwrap()
}
#[test]
fn passes_when_mean_within_range() {
let df = make_f64_df(&[Some(5.0), Some(7.0), Some(9.0)]); let validator = MeanBetweenValidator { min: 6.0, max: 8.0 };
let report = validator.validate(&df, "col").unwrap();
assert_eq!(report.status, "pass");
assert!(report.details.is_none());
}
#[test]
fn fails_when_mean_below_min() {
let df = make_f64_df(&[Some(1.0), Some(2.0), Some(3.0)]); let validator = MeanBetweenValidator {
min: 3.5,
max: 10.0,
};
let report = validator.validate(&df, "col").unwrap();
assert_eq!(report.status, "fail");
assert!(report.details.unwrap().contains("observed_mean=2.00"));
}
#[test]
fn fails_when_mean_above_max() {
let df = make_f64_df(&[Some(10.0), Some(20.0), Some(30.0)]); let validator = MeanBetweenValidator {
min: 0.0,
max: 15.0,
};
let report = validator.validate(&df, "col").unwrap();
assert_eq!(report.status, "fail");
assert!(report.details.unwrap().contains("observed_mean=20.00"));
}
#[test]
fn skips_when_column_not_numeric() {
let df = make_str_df(&[Some("a"), Some("b")]);
let validator = MeanBetweenValidator { min: 0.0, max: 1.0 };
let report = validator.validate(&df, "col").unwrap();
assert_eq!(report.status, "skipped");
assert!(report.details.unwrap().contains("could not be cast"));
}
#[test]
fn skips_when_all_nulls() {
let df = make_f64_df(&[None, None, None]);
let validator = MeanBetweenValidator { min: 0.0, max: 1.0 };
let report = validator.validate(&df, "col").unwrap();
assert_eq!(report.status, "skipped");
assert!(report.details.unwrap().contains("no non-null values"));
}
#[test]
fn skips_when_empty_column() {
let s: Series = Series::new("col".into(), Vec::<Option<f64>>::new());
let df = DataFrame::new(vec![s.into()]).unwrap();
let validator = MeanBetweenValidator { min: 0.0, max: 1.0 };
let report = validator.validate(&df, "col").unwrap();
assert_eq!(report.status, "skipped");
assert!(report.details.unwrap().contains("no non-null values"));
}
}