From 2fc2355fc3d72cbf1ffdc982a42090ada901d21f Mon Sep 17 00:00:00 2001
From: antlilja <liljaanton2001@gmail.com>
Date: Tue, 23 Jun 2020 18:05:32 +0200
Subject: Add expectWithinMargin and test

---
 lib/std/testing.zig | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

(limited to 'lib/std/testing.zig')

diff --git a/lib/std/testing.zig b/lib/std/testing.zig
index 2d136d56c9..9dca969f45 100644
--- a/lib/std/testing.zig
+++ b/lib/std/testing.zig
@@ -168,6 +168,32 @@ test "expectEqual.union(enum)" {
     expectEqual(a10, a10);
 }
 
+/// This function is intended to be used only in tests. When the actual value is not
+/// within the margin of the expected value,
+/// prints diagnostics to stderr to show exactly how they are not equal, then aborts.
+/// The types must be floating point
+pub fn expectWithinMargin(expected: var, actual: @TypeOf(expected), margin: @TypeOf(expected)) void {
+    std.debug.assert(margin >= 0.0);
+
+    switch (@typeInfo(@TypeOf(actual))) {
+        .Float,
+        .ComptimeFloat,
+        => {
+            if (@fabs(expected - actual) > margin) {
+                std.debug.panic("actual {}, not within margin {} of expected {}", .{ actual, margin, expected });
+            }
+        },
+        else => @compileError("Unable to compare non floating point values"),
+    }
+}
+
+test "expectWithinMargin.f32" {
+    const x: f32 = 12.0;
+    const y: f32 = 12.06;
+
+    expectWithinMargin(x, y, 0.1);
+}
+
 /// This function is intended to be used only in tests. When the two slices are not
 /// equal, prints diagnostics to stderr to show exactly how they are not equal,
 /// then aborts.
-- 
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