Add unit tests.

Author: markrogoyski

tests/Probability/Distribution/Continuous/NoncentralTTest.php

@@ -228,6 +228,8 @@ public function testMedian(int $ν, float $μ, float $expected)
     /**
      * @return array [ν, μ, median]
      * Data generated from SciPy: stats.nct(df, nc).ppf(0.5)
+     * Covers edge cases, small/large degrees of freedom, and positive/negative noncentrality parameters
+     * Parameter combinations selected to work within CDF numerical stability limits
      */
     public function dataProviderForMedian(): array
     {
@@ -239,6 +241,53 @@ public function dataProviderForMedian(): array
             [3, 2, 2.2038266580],
             [5, 5, 5.3311221227],
             [1, 1, 1.3202130994],
+
+            // Edge cases with small degrees of freedom
+            [1, 0, 0.0000000000],
+            [1, -1, -1.3202130994],
+            [1, 2, 2.8090503337],
+            [2, 0, 0.0000000000],
+            [2, 1, 1.1424180718],
+            [2, -1, -1.1424180718],
+
+            // Small to medium degrees of freedom with various μ
+            [3, 0, 0.0000000000],
+            [3, -2, -2.2038266580],
+            [3, 1, 1.0911525466],
+            [5, 0, 0.0000000000],
+            [5, -3, -3.1832518216],
+            [5, 3, 3.1832518216],
+
+            // Medium degrees of freedom
+            [7, 4, 4.1754192166],
+            [7, -3, -3.1254551455],
+            [10, -3, -3.0846277081],
+            [10, 0, 0.0000000000],
+            [10, 5, 5.1526842648],
+            [10, -4, -4.1179351977],
+            [15, 2, 2.0350081771],
+            [15, -5, -5.0977309360],
+            [15, 7, 7.1438322816],
+
+            // Larger degrees of freedom
+            [20, 3, 3.0401656737],
+            [20, -6, -6.0880734585],
+            [20, 8, 8.1224601549],
+            [25, 5, 5.0560874073],
+            [25, -8, -8.0961449024],
+            [25, 10, 10.1238625718],
+            [30, 6, 6.0567254706],
+            [30, -10, -10.1017871668],
+
+            // Very large degrees of freedom
+            [50, 0, 0.0000000000],
+            [50, 12, 12.0722582854],
+            [75, 8, 8.0294150239],
+            [75, -12, -12.0467103655],
+            [100, 1, 1.0025072838],
+            [100, -2, -2.0050392625],
+            [100, 5, 5.0129843046],
+            [100, -10, -10.0278449401],
         ];
     }
 }