Make *Fit do not accept flat time series (#113)

* Fix #112

* Fix never-run tests

Author: hombit

CHANGELOG.md

@@ -26,7 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
---
+- **Breaking:** {Bazin,Villar}Fit requires variability now and do not accept flat time series anymore https://github.com/light-curve/light-curve-feature/issues/112 https://github.com/light-curve/light-curve-feature/pull/113
 
 ### Security
 

src/features/bazin_fit.rs

@@ -108,8 +108,8 @@ lazy_info!(
     t_required: true,
     m_required: true,
     w_required: true,
-    sorting_required: true, // improve reproducibility
-    variability_required: false,
+    sorting_required: true, // improves reproducibility
+    variability_required: true,
 );
 
 struct Params<'a, T> {
@@ -419,13 +419,22 @@ mod tests {
     check_feature!(BazinFit);
 
     feature_test!(
-        bazin_fit_plateau,
+        bazin_fit_almost_plateau,
         [BazinFit::default()],
         [0.0, 0.0, 10.0, 5.0, 5.0, 0.0], // initial model parameters and zero chi2
         linspace(0.0, 10.0, 11),
-        [0.0; 11],
+        linspace(0.0, 1e-100, 11), // make it a bit non-flat
     );
 
+    #[test]
+    fn bazin_fit_plateau() {
+        let fe = BazinFit::default();
+        let t = linspace(0.0, 10.0, 11);
+        let f = [0.0; 11];
+        let mut ts = TimeSeries::new_without_weight(&t, &f);
+        assert!(fe.eval(&mut ts).is_err());
+    }
+
     fn bazin_fit_noisy(eval: BazinFit) {
         const N: usize = 50;
 

src/features/villar_fit.rs

@@ -126,8 +126,8 @@ lazy_info!(
     t_required: true,
     m_required: true,
     w_required: true,
-    sorting_required: true, // improve reproducibility
-    variability_required: false,
+    sorting_required: true, // improves reproducibility
+    variability_required: true,
 );
 
 impl<T, U> FitModelTrait<T, U, NPARAMS> for VillarFit
@@ -610,13 +610,22 @@ mod tests {
     check_feature!(VillarFit);
 
     feature_test!(
-        villar_fit_plateau,
+        villar_fit_almost_plateau,
         [VillarFit::default()],
         [0.0, 0.0, 10.0, 5.0, 5.0, 0.0, 1.0, 0.0], // initial model parameters and zero chi2
         linspace(0.0, 10.0, 11),
-        [0.0; 11],
+        linspace(0.0, 1e-100, 11), // make it a bit non-flat
     );
 
+    #[test]
+    fn villar_fit_plateau() {
+        let fe = VillarFit::default();
+        let t = linspace(0.0, 10.0, 11);
+        let f = [0.0; 11];
+        let mut ts = TimeSeries::new_without_weight(&t, &f);
+        assert!(fe.eval(&mut ts).is_err());
+    }
+
     #[cfg(any(
         feature = "gsl",
         any(feature = "ceres-source", feature = "ceres-system")