Add test for min_t_formation_Myr in test_UVLFs.py

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Co-authored-by: JulianBMunoz <22434409+JulianBMunoz@users.noreply.github.com>

Author: Copilot

tests/test_UVLFs.py

@@ -138,4 +138,67 @@ def test_UVLF_binned():
     assert uvlf_nodust.shape == (3,)
 
     # Without dust, we expect different values than with dust
-    assert not np.array_equal(uvlf, uvlf_nodust)
+    assert not np.array_equal(uvlf, uvlf_nodust)
+
+
+def test_UVLF_binned_with_min_t_formation():
+    """Test that min_t_formation_Myr produces finite outputs and suppresses the bright end.
+
+    When sigmaUV is large, scatter can push small halos into unphysically bright bins.
+    Setting min_t_formation_Myr places a physical upper limit on each halo's SFR based on
+    its maximum stellar mass (all baryons converted to stars) and the minimum formation time.
+    This should suppress the very bright end of the UVLF without affecting the faint end.
+    """
+    UserParams = zeus21.User_Parameters()
+    CosmoParams_input = zeus21.Cosmo_Parameters_Input(kmax_CLASS=10., zmax_CLASS=20.)
+    ClassyCosmo = zeus21.runclass(CosmoParams_input)
+    CosmoParams = zeus21.Cosmo_Parameters(UserParams, CosmoParams_input, ClassyCosmo)
+    HMFintclass = zeus21.HMF_interpolator(UserParams, CosmoParams, ClassyCosmo)
+
+    # Use a large sigmaUV to create unphysical scatter into the bright end
+    large_sigmaUV = 2.0
+    min_t_Myr = 10.0
+
+    # AstroParams with the physicality cutoff applied
+    AstroParams_cut = zeus21.Astro_Parameters(
+        UserParams, CosmoParams,
+        sigmaUV=large_sigmaUV,
+        min_t_formation_Myr=min_t_Myr
+    )
+
+    # AstroParams without the cutoff (default None)
+    AstroParams_nocut = zeus21.Astro_Parameters(
+        UserParams, CosmoParams,
+        sigmaUV=large_sigmaUV
+    )
+
+    z_center = 6.0
+    z_width = 0.5
+    # Include a very bright bin (-25) where small-halo scatter is cut off,
+    # a typical bin (-20), and a faint bin (-15) that should be unaffected
+    MUV_centers = np.array([-25.0, -20.0, -15.0])
+    MUV_widths = np.full_like(MUV_centers, 1.0)
+
+    uvlf_cut = UVLF_binned(
+        AstroParams_cut, CosmoParams, HMFintclass,
+        z_center, z_width, MUV_centers, MUV_widths,
+        DUST_FLAG=False, RETURNBIAS=False
+    )
+    uvlf_nocut = UVLF_binned(
+        AstroParams_nocut, CosmoParams, HMFintclass,
+        z_center, z_width, MUV_centers, MUV_widths,
+        DUST_FLAG=False, RETURNBIAS=False
+    )
+
+    # Output must be finite (no NaNs or Infs) with the cutoff applied
+    assert np.all(np.isfinite(uvlf_cut)), "UVLF with min_t_formation_Myr cutoff contains NaN or Inf values"
+
+    # All values must be non-negative
+    assert np.all(uvlf_cut >= 0.0), "UVLF with min_t_formation_Myr cutoff contains negative values"
+
+    # The cutoff should suppress the very bright end: small halos that could not
+    # physically produce MUV=-25 galaxies (min_MUV~-18.7 for 1e8 Msun with t_min=10 Myr)
+    # no longer contribute via scatter, so the bright-end UVLF should be lower
+    assert uvlf_cut[0] < uvlf_nocut[0], (
+        "min_t_formation_Myr cutoff should suppress the very bright end (MUV=-25) of the UVLF"
+    )