From b52c6ee7183917502927b14f641fb5eeb4ce0710 Mon Sep 17 00:00:00 2001
From: Maas Lalani <maaslalani0@gmail.com>
Date: Sun, 8 Aug 2021 14:00:02 -0400
Subject: [PATCH] Add physics test

---
 physics/physics_test.go | 132 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 physics/physics_test.go

diff --git a/physics/physics_test.go b/physics/physics_test.go
new file mode 100644
index 0000000..a7b4e9f
--- /dev/null
+++ b/physics/physics_test.go
@@ -0,0 +1,132 @@
+package physics_test
+
+import (
+	"testing"
+
+	. "github.com/maaslalani/confetty/physics"
+)
+
+func TestNew(t *testing.T) {
+	x := 8
+	y := 20
+
+	physics := New(Point{float64(x), float64(y)}, Vector{1, 1}, Vector(Gravity), 60)
+	if x != physics.PosX() {
+		t.Fatal("x coordinate unexpected")
+	}
+
+	if y != physics.PosY() {
+		t.Fatal("y coordinate unexpected")
+	}
+}
+
+func TestUpdate(t *testing.T) {
+	fps := 60
+	physics := New(Point{0, 0}, Vector{5, 5}, Vector(Gravity), float64(fps))
+
+	// coordinates is the location at which the object should be
+	// after i+1 seconds of simulation.
+	coordinates := []Point{
+		{5, 10},
+		{10, 29},
+		{15, 59},
+		{20, 98},
+		{25, 147},
+		{30, 206},
+		{35, 275},
+	}
+
+	for _, c := range coordinates {
+		// 1 second of simulation
+		for i := 0; i < fps; i++ {
+			physics.Update()
+		}
+
+		x := physics.PosX()
+		y := physics.PosY()
+
+		if x != int(c.X) {
+			t.Logf("Want: %d, Got: %d", x, int(c.X))
+			t.Fatal("x coordinate unexpected")
+		}
+		if y != int(c.Y) {
+			t.Logf("Want: %d, Got: %d", y, int(c.Y))
+			t.Fatal("y coordinate unexpected")
+		}
+	}
+}
+
+func TestDisplacement(t *testing.T) {
+	tt := []struct {
+		x   int
+		y   int
+		vel Vector
+		d   float64
+	}{
+		{x: 5, y: 5, vel: Vector{5, 10}, d: 11.180339887498933},
+		{x: 0, y: 0, vel: Vector{1, 1}, d: 1.414213562373097},
+	}
+
+	fps := 60
+
+	for _, tc := range tt {
+		physics := New(Point{float64(tc.x), float64(tc.y)}, tc.vel, Vector{}, float64(fps))
+
+		// 1 second of simulation
+		for i := 0; i < fps; i++ {
+			physics.Update()
+		}
+
+		if physics.Displacement() != tc.d {
+			t.Log(physics.Displacement())
+			t.Fatal("expected displacement to be 15")
+		}
+	}
+}
+
+func TestReset(t *testing.T) {
+	x := 5
+	y := 10
+	vel := Vector{20, 20}
+	fps := 60
+
+	physics := New(Point{float64(x), float64(y)}, vel, Vector(Gravity), float64(fps))
+
+	// 1 second of simulation
+	for i := 0; i < fps; i++ {
+		physics.Update()
+	}
+
+	// store the current position after 1 second of simulation we will simulate 1
+	// second again and ensure that the object reaches the same position, we
+	// don't care what the position is but if the object reaches the same
+	// position again then we ensure that the velocity and acceleration was reset
+	cx := physics.PosX()
+	cy := physics.PosY()
+
+	physics.Reset()
+
+	if physics.PosX() != x {
+		t.Fatal("expected x to be reset")
+	}
+
+	if physics.PosY() != y {
+		t.Fatal("expected y to be reset")
+	}
+
+	// 1 second of simulation
+	// here we are simply checking that the object reaches the same position
+	// after being reset in the same amount of time. This ensures velocity and
+	// acceleration were reset without checking them explicitly
+	for i := 0; i < fps; i++ {
+		physics.Update()
+	}
+
+	if physics.PosX() != cx {
+		t.Fatal("expected simulation to be repeatable")
+	}
+
+	if physics.PosY() != cy {
+		t.Fatal("expected simulation to be repeatable")
+	}
+}