Meaning of delta or epsilon argument of assertEquals for double values

java junit floating-point
Édipo Féderle picture Édipo Féderle · Apr 16, 2011 · Viewed 156.1k times · Source

I have a question about JUnit assertEquals to test double values. Reading the API doc I can see:

@Deprecated
public static void assertEquals(double expected, double actual)

Deprecated. Use assertEquals(double expected, double actual, double delta) instead.

(Note: in older documentation versions, the delta parameter is called epsilon)

What does the delta (or epsilon) parameter mean?

Answer

jberg picture jberg · Apr 16, 2011

Epsilon is the value that the 2 numbers can be off by. So it will assert to true as long as Math.abs(expected - actual) < epsilon

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