A white box, in contrast to a black box, is a subsystem whose internals can be viewed, but usually cannot be altered.
Having access to the subsystem internals in general makes the subsystem easier to understand, but also easier to hack; if a programmer, for example, can examine source code, weaknesses in an algorithm are much easier to discover. This makes white box testing much more effective than black box testing, but considerably more difficult due to the sophistication needed on the part of the tester to understand the subsystem.
Also known as glass box, clear box, or open box.
In practice some white box systems are so complex that it might as well be a Black box.
Famous quotes containing the words white and/or box:
“Slavery is no scholar, no improver; it does not love the whistle of the railroad; it does not love the newspaper, the mail-bag, a college, a book or a preacher who has the absurd whim of saying what he thinks; it does not increase the white population; it does not improve the soil; everything goes to decay.”
—Ralph Waldo Emerson (1803–1882)
“I hate love. Hate being in love. I never want it to happen to me again.”
—Muriel Box (b. 1905)