# HG changeset patch
# User Nolan Prescott <mail@nprescott.com>
# Date 1584727234 14400
#      Fri Mar 20 14:00:34 2020 -0400
# Node ID 15e9ba623ebd4bb236506cbb7d30304199d7bd86
# Parent  c9136f86c700ea76e2b4154b0928ebd5e2d428db
a few more matrix inverse tests

diff --git a/tracer.lisp b/tracer.lisp
--- a/tracer.lisp
+++ b/tracer.lisp
@@ -489,6 +489,26 @@
                          (   -3/38   -17/76   -1/19   15/76)
                          (-139/266 -433/532 -40/133 163/532))))))
 
+(deftest inverse-is-reversible
+  (let* ((a #2A((-5  2  6 -8)
+                ( 1 -5  1  8)
+                ( 7  7 -6 -7)
+                ( 1 -3  7  4)))
+         (b (inverse a)))
+    (check (equalp (inverse b) a))))
+
+(deftest inverse-undoes-multiplication
+  (let* ((a #2A(( 3 -9  7  3)
+                ( 3 -8  2 -9)
+                (-4  4  4  1)
+                (-6  5 -1  1)))
+         (b #2A((8  2 2 2)
+                (3 -1 7 0)
+                (7  0 5 4)
+                (6 -2 0 5)))
+         (c (matrix*matrix a b)))
+    (check (equalp (matrix*matrix c (inverse b)) a))))
+
 (deftest matrix-basics
   (multiply-4x4-matrices)
   (multiply-matrix-with-vector)
@@ -505,7 +525,9 @@
   (4x4-matrix-determinant)
   (invertibility-predicate)
   (invertibility-negative-case)
-  (calculate-matrix-inverse))
+  (calculate-matrix-inverse)
+  (inverse-is-reversible)
+  (inverse-undoes-multiplication))
 
 (deftest suite
   (vector-basics)