From ffcb15d3f25ebc25ee0dab68fadfe5e88e2b755f Mon Sep 17 00:00:00 2001
From: dizcza <dizcza@gmail.com>
Date: Sat, 8 Aug 2020 21:07:10 +0200
Subject: added tests

---
 .circleci/config.yml |  35 ++++++++
 README               |  12 ---
 README.md            |  15 ++++
 linmath.h            | 139 ++++++++++++++---------------
 linmath_test.c       |   9 ++
 linmath_test.h       | 242 +++++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 364 insertions(+), 88 deletions(-)
 create mode 100644 .circleci/config.yml
 delete mode 100644 README
 create mode 100644 README.md
 create mode 100644 linmath_test.c
 create mode 100644 linmath_test.h

diff --git a/.circleci/config.yml b/.circleci/config.yml
new file mode 100644
index 0000000..17987bb
--- /dev/null
+++ b/.circleci/config.yml
@@ -0,0 +1,35 @@
+version: 2.1
+
+jobs:
+  linmath-test:
+    machine:
+      image: ubuntu-1604:201903-01
+    steps:
+     - run: gcc --version
+     - checkout
+     - run:
+         command: |
+           gcc -O0 -o linmath_test.o linmath_test.c -lm
+           ./linmath_test.o
+         name: linmath tests gcc -O0
+     - run:
+         command: |
+           gcc -O1 -o linmath_test.o linmath_test.c -lm
+           ./linmath_test.o
+         name: linmath tests gcc -O1
+     - run:
+         command: |
+           gcc -O2 -o linmath_test.o linmath_test.c -lm
+           ./linmath_test.o
+         name: linmath tests gcc -O2
+     - run:
+         command: |
+           gcc -O3 -o linmath_test.o linmath_test.c -lm
+           ./linmath_test.o
+         name: linmath tests gcc -O3
+
+
+workflows:
+  main:
+    jobs:
+      - linmath-test
diff --git a/README b/README
deleted file mode 100644
index a61a9e0..0000000
--- a/README
+++ /dev/null
@@ -1,12 +0,0 @@
-# linmath.h -- A small library for linear math as required for computer graphics
-
-linmath.h provides the most used types required for programming computer graphics:
-
-vec3 -- 3 element vector of floats
-vec4 -- 4 element vector of floats (4th component used for homogenous computations)
-mat4x4 -- 4 by 4 elements matrix, computations are done in column major order
-quat -- quaternion
-
-The types are deliberately named like the types in GLSL. In fact they are meant to
-be used for the client side computations and passing to same typed GLSL uniforms.
-
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..7a06566
--- /dev/null
+++ b/README.md
@@ -0,0 +1,15 @@
+# linmath.h -- A small library for linear math as required for computer graphics
+
+[![CircleCI](https://circleci.com/gh/datenwolf/linmath.h.svg?style=svg)](https://app.circleci.com/pipelines/github/datenwolf/linmath.h)
+
+
+linmath.h provides the most used types required for programming computer graphics:
+
+vec3 -- 3 element vector of floats
+vec4 -- 4 element vector of floats (4th component used for homogenous computations)
+mat4x4 -- 4 by 4 elements matrix, computations are done in column major order
+quat -- quaternion
+
+The types are deliberately named like the types in GLSL. In fact they are meant to
+be used for the client side computations and passing to same typed GLSL uniforms.
+
diff --git a/linmath.h b/linmath.h
index 2a92211..aaa3e1e 100644
--- a/linmath.h
+++ b/linmath.h
@@ -1,6 +1,7 @@
 #ifndef LINMATH_H
 #define LINMATH_H
 
+#include <string.h>
 #include <math.h>
 
 #ifdef LINMATH_NO_INLINE
@@ -31,7 +32,7 @@ LINMATH_H_FUNC void vec##n##_scale(vec##n r, vec##n const v, float const s) \
 } \
 LINMATH_H_FUNC float vec##n##_mul_inner(vec##n const a, vec##n const b) \
 { \
-	float p = 0.; \
+	float p = 0.f; \
 	int i; \
 	for(i=0; i<n; ++i) \
 		p += b[i]*a[i]; \
@@ -43,7 +44,7 @@ LINMATH_H_FUNC float vec##n##_len(vec##n const v) \
 } \
 LINMATH_H_FUNC void vec##n##_norm(vec##n r, vec##n const v) \
 { \
-	float k = 1.0 / vec##n##_len(v); \
+	float k = 1.f / vec##n##_len(v); \
 	vec##n##_scale(r, v, k); \
 } \
 LINMATH_H_FUNC void vec##n##_min(vec##n r, vec##n const a, vec##n const b) \
@@ -57,6 +58,12 @@ LINMATH_H_FUNC void vec##n##_max(vec##n r, vec##n const a, vec##n const b) \
 	int i; \
 	for(i=0; i<n; ++i) \
 		r[i] = a[i]>b[i] ? a[i] : b[i]; \
+} \
+LINMATH_H_FUNC void vec##n##_dup(vec##n r, vec##n const src) \
+{ \
+	int i; \
+	for(i=0; i<n; ++i) \
+		r[i] = src[i]; \
 }
 
 LINMATH_H_DEFINE_VEC(2)
@@ -78,7 +85,7 @@ LINMATH_H_FUNC void vec3_reflect(vec3 r, vec3 const v, vec3 const n)
 		r[i] = v[i] - p*n[i];
 }
 
-LINMATH_H_FUNC void vec4_mul_cross(vec4 r, vec4 a, vec4 b)
+LINMATH_H_FUNC void vec4_mul_cross(vec4 r, vec4 const a, vec4 const b)
 {
 	r[0] = a[1]*b[2] - a[2]*b[1];
 	r[1] = a[2]*b[0] - a[0]*b[2];
@@ -86,7 +93,7 @@ LINMATH_H_FUNC void vec4_mul_cross(vec4 r, vec4 a, vec4 b)
 	r[3] = 1.f;
 }
 
-LINMATH_H_FUNC void vec4_reflect(vec4 r, vec4 v, vec4 n)
+LINMATH_H_FUNC void vec4_reflect(vec4 r, vec4 const v, vec4 const n)
 {
 	float p  = 2.f*vec4_mul_inner(v, n);
 	int i;
@@ -102,61 +109,59 @@ LINMATH_H_FUNC void mat4x4_identity(mat4x4 M)
 		for(j=0; j<4; ++j)
 			M[i][j] = i==j ? 1.f : 0.f;
 }
-LINMATH_H_FUNC void mat4x4_dup(mat4x4 M, mat4x4 N)
+LINMATH_H_FUNC void mat4x4_dup(mat4x4 M, mat4x4 const N)
 {
-	int i, j;
+	int i;
 	for(i=0; i<4; ++i)
-		for(j=0; j<4; ++j)
-			M[i][j] = N[i][j];
+		vec4_dup(M[i], N[i]);
 }
-LINMATH_H_FUNC void mat4x4_row(vec4 r, mat4x4 M, int i)
+LINMATH_H_FUNC void mat4x4_row(vec4 r, mat4x4 const M, int i)
 {
 	int k;
 	for(k=0; k<4; ++k)
 		r[k] = M[k][i];
 }
-LINMATH_H_FUNC void mat4x4_col(vec4 r, mat4x4 M, int i)
+LINMATH_H_FUNC void mat4x4_col(vec4 r, mat4x4 const M, int i)
 {
 	int k;
 	for(k=0; k<4; ++k)
 		r[k] = M[i][k];
 }
-LINMATH_H_FUNC void mat4x4_transpose(mat4x4 M, mat4x4 N)
+LINMATH_H_FUNC void mat4x4_transpose(mat4x4 M, mat4x4 const N)
 {
+    // Note: if M and N are the same, the user has to
+    // explicitly make a copy of M and set it to N.
 	int i, j;
 	for(j=0; j<4; ++j)
 		for(i=0; i<4; ++i)
 			M[i][j] = N[j][i];
 }
-LINMATH_H_FUNC void mat4x4_add(mat4x4 M, mat4x4 a, mat4x4 b)
+LINMATH_H_FUNC void mat4x4_add(mat4x4 M, mat4x4 const a, mat4x4 const b)
 {
 	int i;
 	for(i=0; i<4; ++i)
 		vec4_add(M[i], a[i], b[i]);
 }
-LINMATH_H_FUNC void mat4x4_sub(mat4x4 M, mat4x4 a, mat4x4 b)
+LINMATH_H_FUNC void mat4x4_sub(mat4x4 M, mat4x4 const a, mat4x4 const b)
 {
 	int i;
 	for(i=0; i<4; ++i)
 		vec4_sub(M[i], a[i], b[i]);
 }
-LINMATH_H_FUNC void mat4x4_scale(mat4x4 M, mat4x4 a, float k)
+LINMATH_H_FUNC void mat4x4_scale(mat4x4 M, mat4x4 const a, float k)
 {
 	int i;
 	for(i=0; i<4; ++i)
 		vec4_scale(M[i], a[i], k);
 }
-LINMATH_H_FUNC void mat4x4_scale_aniso(mat4x4 M, mat4x4 a, float x, float y, float z)
+LINMATH_H_FUNC void mat4x4_scale_aniso(mat4x4 M, mat4x4 const a, float x, float y, float z)
 {
-	int i;
 	vec4_scale(M[0], a[0], x);
 	vec4_scale(M[1], a[1], y);
 	vec4_scale(M[2], a[2], z);
-	for(i = 0; i < 4; ++i) {
-		M[3][i] = a[3][i];
-	}
+	vec4_dup(M[3], a[3]);
 }
-LINMATH_H_FUNC void mat4x4_mul(mat4x4 M, mat4x4 a, mat4x4 b)
+LINMATH_H_FUNC void mat4x4_mul(mat4x4 M, mat4x4 const a, mat4x4 const b)
 {
 	mat4x4 temp;
 	int k, r, c;
@@ -167,7 +172,7 @@ LINMATH_H_FUNC void mat4x4_mul(mat4x4 M, mat4x4 a, mat4x4 b)
 	}
 	mat4x4_dup(M, temp);
 }
-LINMATH_H_FUNC void mat4x4_mul_vec4(vec4 r, mat4x4 M, vec4 v)
+LINMATH_H_FUNC void mat4x4_mul_vec4(vec4 r, mat4x4 const M, vec4 const v)
 {
 	int i, j;
 	for(j=0; j<4; ++j) {
@@ -193,13 +198,13 @@ LINMATH_H_FUNC void mat4x4_translate_in_place(mat4x4 M, float x, float y, float
 		M[3][i] += vec4_mul_inner(r, t);
 	}
 }
-LINMATH_H_FUNC void mat4x4_from_vec3_mul_outer(mat4x4 M, vec3 a, vec3 b)
+LINMATH_H_FUNC void mat4x4_from_vec3_mul_outer(mat4x4 M, vec3 const a, vec3 const b)
 {
 	int i, j;
 	for(i=0; i<4; ++i) for(j=0; j<4; ++j)
 		M[i][j] = i<3 && j<3 ? a[i] * b[j] : 0.f;
 }
-LINMATH_H_FUNC void mat4x4_rotate(mat4x4 R, mat4x4 M, float x, float y, float z, float angle)
+LINMATH_H_FUNC void mat4x4_rotate(mat4x4 R, mat4x4 const M, float x, float y, float z, float angle)
 {
 	float s = sinf(angle);
 	float c = cosf(angle);
@@ -227,13 +232,13 @@ LINMATH_H_FUNC void mat4x4_rotate(mat4x4 R, mat4x4 M, float x, float y, float z,
 		mat4x4_add(T, T, C);
 		mat4x4_add(T, T, S);
 
-		T[3][3] = 1.;		
+		T[3][3] = 1.f;
 		mat4x4_mul(R, M, T);
 	} else {
 		mat4x4_dup(R, M);
 	}
 }
-LINMATH_H_FUNC void mat4x4_rotate_X(mat4x4 Q, mat4x4 M, float angle)
+LINMATH_H_FUNC void mat4x4_rotate_X(mat4x4 Q, mat4x4 const M, float angle)
 {
 	float s = sinf(angle);
 	float c = cosf(angle);
@@ -245,7 +250,7 @@ LINMATH_H_FUNC void mat4x4_rotate_X(mat4x4 Q, mat4x4 M, float angle)
 	};
 	mat4x4_mul(Q, M, R);
 }
-LINMATH_H_FUNC void mat4x4_rotate_Y(mat4x4 Q, mat4x4 M, float angle)
+LINMATH_H_FUNC void mat4x4_rotate_Y(mat4x4 Q, mat4x4 const M, float angle)
 {
 	float s = sinf(angle);
 	float c = cosf(angle);
@@ -257,7 +262,7 @@ LINMATH_H_FUNC void mat4x4_rotate_Y(mat4x4 Q, mat4x4 M, float angle)
 	};
 	mat4x4_mul(Q, M, R);
 }
-LINMATH_H_FUNC void mat4x4_rotate_Z(mat4x4 Q, mat4x4 M, float angle)
+LINMATH_H_FUNC void mat4x4_rotate_Z(mat4x4 Q, mat4x4 const M, float angle)
 {
 	float s = sinf(angle);
 	float c = cosf(angle);
@@ -269,7 +274,7 @@ LINMATH_H_FUNC void mat4x4_rotate_Z(mat4x4 Q, mat4x4 M, float angle)
 	};
 	mat4x4_mul(Q, M, R);
 }
-LINMATH_H_FUNC void mat4x4_invert(mat4x4 T, mat4x4 M)
+LINMATH_H_FUNC void mat4x4_invert(mat4x4 T, mat4x4 const M)
 {
 	float s[6];
 	float c[6];
@@ -310,10 +315,10 @@ LINMATH_H_FUNC void mat4x4_invert(mat4x4 T, mat4x4 M)
 	T[3][2] = (-M[3][0] * s[3] + M[3][1] * s[1] - M[3][2] * s[0]) * idet;
 	T[3][3] = ( M[2][0] * s[3] - M[2][1] * s[1] + M[2][2] * s[0]) * idet;
 }
-LINMATH_H_FUNC void mat4x4_orthonormalize(mat4x4 R, mat4x4 M)
+LINMATH_H_FUNC void mat4x4_orthonormalize(mat4x4 R, mat4x4 const M)
 {
 	mat4x4_dup(R, M);
-	float s = 1.;
+	float s = 1.f;
 	vec3 h;
 
 	vec3_norm(R[2], R[2]);
@@ -338,7 +343,7 @@ LINMATH_H_FUNC void mat4x4_frustum(mat4x4 M, float l, float r, float b, float t,
 	M[0][0] = 2.f*n/(r-l);
 	M[0][1] = M[0][2] = M[0][3] = 0.f;
 	
-	M[1][1] = 2.*n/(t-b);
+	M[1][1] = 2.f*n/(t-b);
 	M[1][0] = M[1][2] = M[1][3] = 0.f;
 
 	M[2][0] = (r+l)/(r-l);
@@ -369,7 +374,7 @@ LINMATH_H_FUNC void mat4x4_perspective(mat4x4 m, float y_fov, float aspect, floa
 {
 	/* NOTE: Degrees are an unhandy unit to work with.
 	 * linmath.h uses radians for everything! */
-	float const a = 1.f / tan(y_fov / 2.f);
+	float const a = 1.f / tanf(y_fov / 2.f);
 
 	m[0][0] = a / aspect;
 	m[0][1] = 0.f;
@@ -391,7 +396,7 @@ LINMATH_H_FUNC void mat4x4_perspective(mat4x4 m, float y_fov, float aspect, floa
 	m[3][2] = -((2.f * f * n) / (f - n));
 	m[3][3] = 0.f;
 }
-LINMATH_H_FUNC void mat4x4_look_at(mat4x4 m, vec3 eye, vec3 center, vec3 up)
+LINMATH_H_FUNC void mat4x4_look_at(mat4x4 m, vec3 const eye, vec3 const center, vec3 const up)
 {
 	/* Adapted from Android's OpenGL Matrix.java.                        */
 	/* See the OpenGL GLUT documentation for gluLookAt for a description */
@@ -434,24 +439,18 @@ LINMATH_H_FUNC void mat4x4_look_at(mat4x4 m, vec3 eye, vec3 center, vec3 up)
 }
 
 typedef float quat[4];
+#define quat_add vec4_add
+#define quat_sub vec4_sub
+#define quat_norm vec4_norm
+#define quat_scale vec4_scale
+#define quat_mul_inner vec4_mul_inner
+
 LINMATH_H_FUNC void quat_identity(quat q)
 {
 	q[0] = q[1] = q[2] = 0.f;
 	q[3] = 1.f;
 }
-LINMATH_H_FUNC void quat_add(quat r, quat a, quat b)
-{
-	int i;
-	for(i=0; i<4; ++i)
-		r[i] = a[i] + b[i];
-}
-LINMATH_H_FUNC void quat_sub(quat r, quat a, quat b)
-{
-	int i;
-	for(i=0; i<4; ++i)
-		r[i] = a[i] - b[i];
-}
-LINMATH_H_FUNC void quat_mul(quat r, quat p, quat q)
+LINMATH_H_FUNC void quat_mul(quat r, quat const p, quat const q)
 {
 	vec3 w;
 	vec3_mul_cross(r, p, q);
@@ -461,37 +460,22 @@ LINMATH_H_FUNC void quat_mul(quat r, quat p, quat q)
 	vec3_add(r, r, w);
 	r[3] = p[3]*q[3] - vec3_mul_inner(p, q);
 }
-LINMATH_H_FUNC void quat_scale(quat r, quat v, float s)
-{
-	int i;
-	for(i=0; i<4; ++i)
-		r[i] = v[i] * s;
-}
-LINMATH_H_FUNC float quat_inner_product(quat a, quat b)
-{
-	float p = 0.f;
-	int i;
-	for(i=0; i<4; ++i)
-		p += b[i]*a[i];
-	return p;
-}
-LINMATH_H_FUNC void quat_conj(quat r, quat q)
+LINMATH_H_FUNC void quat_conj(quat r, quat const q)
 {
 	int i;
 	for(i=0; i<3; ++i)
 		r[i] = -q[i];
 	r[3] = q[3];
 }
-LINMATH_H_FUNC void quat_rotate(quat r, float angle, vec3 axis) {
-	vec3 v;
-	vec3_scale(v, axis, sinf(angle / 2));
-	int i;
-	for(i=0; i<3; ++i)
-		r[i] = v[i];
-	r[3] = cosf(angle / 2);
+LINMATH_H_FUNC void quat_rotate(quat r, float angle, vec3 const axis) {
+    vec3 axis_norm;
+    vec3_norm(axis_norm, axis);
+    float s = sinf(angle / 2);
+    float c = cosf(angle / 2);
+    vec3_scale(r, axis_norm, s);
+    r[3] = c;
 }
-#define quat_norm vec4_norm
-LINMATH_H_FUNC void quat_mul_vec3(vec3 r, quat q, vec3 v)
+LINMATH_H_FUNC void quat_mul_vec3(vec3 r, quat const q, vec3 const v)
 {
 /*
  * Method by Fabian 'ryg' Giessen (of Farbrausch)
@@ -511,7 +495,7 @@ v' = v + q.w * t + cross(q.xyz, t)
 	vec3_add(r, v, t);
 	vec3_add(r, r, u);
 }
-LINMATH_H_FUNC void mat4x4_from_quat(mat4x4 M, quat q)
+LINMATH_H_FUNC void mat4x4_from_quat(mat4x4 M, quat const q)
 {
 	float a = q[3];
 	float b = q[0];
@@ -541,18 +525,21 @@ LINMATH_H_FUNC void mat4x4_from_quat(mat4x4 M, quat q)
 	M[3][3] = 1.f;
 }
 
-LINMATH_H_FUNC void mat4x4o_mul_quat(mat4x4 R, mat4x4 M, quat q)
+LINMATH_H_FUNC void mat4x4o_mul_quat(mat4x4 R, mat4x4 const M, quat const q)
 {
-/*  XXX: The way this is written only works for othogonal matrices. */
+/*  XXX: The way this is written only works for orthogonal matrices. */
 /* TODO: Take care of non-orthogonal case. */
 	quat_mul_vec3(R[0], q, M[0]);
 	quat_mul_vec3(R[1], q, M[1]);
 	quat_mul_vec3(R[2], q, M[2]);
 
 	R[3][0] = R[3][1] = R[3][2] = 0.f;
-	R[3][3] = 1.f;
+	R[0][3] = M[0][3];
+	R[1][3] = M[1][3];
+	R[2][3] = M[2][3];
+	R[3][3] = M[3][3];  // typically 1.0, but here we make it general
 }
-LINMATH_H_FUNC void quat_from_mat4x4(quat q, mat4x4 M)
+LINMATH_H_FUNC void quat_from_mat4x4(quat q, mat4x4 const M)
 {
 	float r=0.f;
 	int i;
@@ -582,7 +569,7 @@ LINMATH_H_FUNC void quat_from_mat4x4(quat q, mat4x4 M)
 	q[3] = (M[p[2]][p[1]] - M[p[1]][p[2]])/(2.f*r);
 }
 
-LINMATH_H_FUNC void mat4x4_arcball(mat4x4 R, mat4x4 M, vec2 _a, vec2 _b, float s)
+LINMATH_H_FUNC void mat4x4_arcball(mat4x4 R, mat4x4 const M, vec2 const _a, vec2 const _b, float s)
 {
 	vec2 a; memcpy(a, _a, sizeof(a));
 	vec2 b; memcpy(b, _b, sizeof(b));
diff --git a/linmath_test.c b/linmath_test.c
new file mode 100644
index 0000000..d7ce1fa
--- /dev/null
+++ b/linmath_test.c
@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+#include "linmath_test.h"
+
+int main() {
+    linmath_test_run_all();
+    printf("linmath tests passed\n");
+    return 0;
+}
diff --git a/linmath_test.h b/linmath_test.h
new file mode 100644
index 0000000..5c48444
--- /dev/null
+++ b/linmath_test.h
@@ -0,0 +1,242 @@
+/*
+ * linmath_test.h
+ *
+ *  Created on: Apr 9, 2017
+ *      Author: Danylo Ulianych
+ */
+
+#ifndef LINMATH_TEST_H
+#define LINMATH_TEST_H
+
+#include <stdlib.h>
+#include "linmath.h"
+
+#define LINMATH_EPS                   (0.0001f)
+#define linmath_is_close(val1, val2)  (fabsf(val1 - val2) < LINMATH_EPS)
+
+#ifndef linmath_assert
+#include <assert.h>
+#define linmath_assert                assert
+#endif /* linmath_assert */
+
+
+static float linmath_random_float() {
+	return rand() / (float) RAND_MAX;
+}
+
+#define LINMATH_TEST_DEFINE_VEC(n) \
+static void linmath_vec##n##_set(vec##n v, float value) { \
+	int i; \
+	for (i=0; i<n; i++) { \
+		v[i] = value; \
+	} \
+} \
+static void linmath_vec##n##_init_random(vec##n v) { \
+	int i; \
+	for (i=0; i<n; i++) { \
+		v[i] = linmath_random_float(); \
+	} \
+} \
+static int linmath_vec##n##_allclose(vec##n const a, vec##n const b) { \
+	int i, equal = 1; \
+	for(i = 0; i < n; ++i) \
+		equal &= linmath_is_close(a[i], b[i]); \
+	return equal; \
+} \
+static void linmath_test_vec##n##_mul_inner() { \
+	/* The inner product of a vector of ones with itself must equal 'n'. */ \
+	vec##n v; \
+	linmath_vec##n##_set(v, 1.0f); \
+	float inner_prod = vec##n##_mul_inner(v, v); \
+	linmath_assert(linmath_is_close(inner_prod, n)); \
+} \
+static void linmath_test_vec##n##_len() { \
+	/* The length of a vector of ones must equal sqrt(n). */ \
+	vec##n v; \
+	int i; \
+	for (i=0; i<n; i++) { \
+		v[i] = 1.0f; \
+	} \
+	float norm = vec##n##_len(v); \
+	linmath_assert(linmath_is_close(norm, sqrtf(n))); \
+} \
+static void linmath_test_vec##n##_norm() { \
+	/* The norm of a normalized vector must be 1.0. */ \
+	srand(17U);  /* set any seed */ \
+	vec##n v; \
+	linmath_vec##n##_init_random(v); \
+	vec##n r; \
+	vec##n##_norm(r, v); \
+	float norm = vec##n##_len(r); \
+	linmath_assert(linmath_is_close(norm, 1.0f)); \
+}
+
+
+LINMATH_TEST_DEFINE_VEC(2);
+LINMATH_TEST_DEFINE_VEC(3);
+LINMATH_TEST_DEFINE_VEC(4);
+
+
+static void linmath_test_vec3_mul_cross() {
+	srand(13U);  /* set any seed */
+	vec3 v1, v2, r;
+	linmath_vec3_init_random(v1);
+	vec3_dup(v2, v1);
+	vec3_mul_cross(r, v1, v2);
+	vec3 v_expected;
+
+	// the cross product of equal vectors must be zero
+	linmath_vec3_set(v_expected, 0.0f);
+	linmath_assert(linmath_vec3_allclose(r, v_expected));
+
+	// test ijk axes cross product
+	vec3 i = {1, 0, 0};
+	vec3 j = {0, 1, 0};
+	vec3 k = {0, 0, 1};
+	vec3_mul_cross(r, i, j);
+	linmath_assert(linmath_vec3_allclose(r, k));
+}
+
+static void linmath_test_vec4_mul_cross() {
+	srand(13U);  /* set any seed */
+	vec4 v1, v2, r;
+	linmath_vec4_init_random(v1);
+	vec4_dup(v2, v1);
+	vec4_mul_cross(r, v1, v2);
+	vec4 v_expected;
+
+	// the cross product of equal vectors must be zero
+	linmath_vec4_set(v_expected, 0.0f);
+	v_expected[3] = 1.0f;
+	linmath_assert(linmath_vec4_allclose(r, v_expected));
+
+	// test ijk axes cross product
+	vec4 i = {1, 0, 0, 1};
+	vec4 j = {0, 1, 0, 1};
+	vec4 k = {0, 0, 1, 1};
+	vec4_mul_cross(r, i, j);
+	linmath_assert(linmath_vec4_allclose(r, k));
+}
+
+
+static int linmath_mat4x4_allclose(mat4x4 const M, mat4x4 const N) {
+	int i, equal = 1;
+	for (i = 0; i < 4; ++i)
+		equal &= linmath_vec4_allclose(M[i], N[i]);
+	return equal;
+}
+
+/**
+ * Test the correctnes of a quaternion creation
+ * that is used as a linear operator to rotate
+ * vectors and matrices (later on).
+ */
+static void linmath_test_quat_rotate() {
+    vec3 axis = {0, 1, 0};
+	quat q;
+	float theta = M_PI_4;
+	quat_rotate(q, theta, axis);
+	quat q_refernce = {0, sinf(theta / 2), 0, cosf(theta / 2)};
+	linmath_assert(linmath_vec4_allclose(q, q_refernce));
+}
+
+/**
+ * The conjugate of a quaternion must correspond to
+ * the rotation with a negative angle.
+ */
+static void linmath_test_quat_conj() {
+    srand(15U);
+	quat q, q_conj, q_reference;
+	vec3 axis = { 0, 1, 0 };
+	float angle_rads = linmath_random_float();
+	quat_rotate(q, angle_rads, axis);
+	quat_conj(q_conj, q);
+	quat_rotate(q_reference, -angle_rads, axis);
+	linmath_assert(linmath_vec4_allclose(q_conj, q_reference));
+}
+
+/* Rotate a vector back and forth. */
+static void linmath_test_quat_mul_vec3() {
+	srand(11U);
+	quat q, q_conj;
+	vec3 axis = { 0, 1, 0 };
+	float angle_rads = linmath_random_float();
+	quat_rotate(q, angle_rads, axis);
+	quat_conj(q_conj, q);
+
+	vec3 v_initial, v_rotated, v_restored;
+	linmath_vec3_init_random(v_initial);
+	quat_mul_vec3(v_rotated, q, v_initial);
+	quat_mul_vec3(v_restored, q_conj, v_rotated);
+	linmath_assert(linmath_vec3_allclose(v_restored, v_initial));
+}
+
+/* Rotate a matrix back and forth. */
+static void linmath_test_mat4x4o_mul_quat() {
+	srand(12U);
+	quat q, q_conj;
+	vec3 axis = { 0, 1, 0 };
+	float angle_rads = linmath_random_float();
+	quat_rotate(q, angle_rads, axis);
+	quat_conj(q_conj, q);
+
+	mat4x4 m_reference, m_rotated, m;
+	mat4x4_identity(m_reference);
+	m_reference[0][3] = 0.1f;
+	m_reference[1][3] = 0.2f;
+	m_reference[2][3] = 0.3f;
+	mat4x4o_mul_quat(m_rotated, m_reference, q);
+	mat4x4o_mul_quat(m, m_rotated, q_conj);
+	linmath_assert(linmath_mat4x4_allclose(m_reference, m));
+}
+
+/**
+ * Test if an extracted quaternion from from a
+ * rotational matrix matches the original one.
+ */
+static void linmath_test_quat_from_mat4x4() {
+	srand(7U);
+	quat q_reference;
+	vec3 axis = { 0, 1, 0 };
+	float angle_rads = linmath_random_float();
+	quat_rotate(q_reference, angle_rads, axis);
+
+	mat4x4 m_identity, m_rotated;
+	mat4x4_identity(m_identity);
+	mat4x4o_mul_quat(m_rotated, m_identity, q_reference);
+
+	quat q_restored;
+	quat_from_mat4x4(q_restored, m_rotated);
+	linmath_assert(linmath_vec4_allclose(q_restored, q_reference));
+}
+
+
+
+static void linmath_test_run_all() {
+
+	linmath_test_vec2_mul_inner();
+	linmath_test_vec3_mul_inner();
+	linmath_test_vec4_mul_inner();
+
+	linmath_test_vec2_len();
+	linmath_test_vec3_len();
+	linmath_test_vec4_len();
+
+	linmath_test_vec2_norm();
+	linmath_test_vec3_norm();
+	linmath_test_vec4_norm();
+
+	linmath_test_vec3_mul_cross();
+	linmath_test_vec4_mul_cross();
+
+	linmath_test_quat_rotate();
+	linmath_test_quat_conj();
+	linmath_test_quat_mul_vec3();
+	linmath_test_mat4x4o_mul_quat();
+
+	/* FIXME: Below is the wrecked functional that does not work */
+    // linmath_test_quat_from_mat4x4();
+}
+
+
+#endif /* LINMATH_TEST_H */
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