Test Knobs

Concept

Test knobs are weighted controls in a constrained-random test interface that let a test writer steer the mix and distribution of generated stimulus, such as opcode categories or instruction types, without directly constraining every low-level instruction field.

First seen 5/28/2026

Last seen 5/28/2026

Evidence 2 chunks

Wiki v1

WIKI

Definition

Test knobs are controls, described in the evidence as “knobs or switches,” that allow a test writer to generate constrained stimulus by steering high-level choices in a random test generator. In the cited opcode-generator architecture, tests provide weighted values that direct the generator toward a required mix of instructions, and the constraint solver applies those weights to control the distribution of generated opcode types.

Use in constrained-random generation

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NEIGHBORHOOD

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RELATIONSHIPS

2 connections

Hierarchical Constrained-Random Test Generation ← uses 90% 2e

The instruction generator is controlled by a set of knobs to direct stimulus generation.

Opcode Generator ← uses 90% 1e

The instruction generator is controlled by a set of knobs allowing test writers to generate constrained stimulus.

LINKED ENTITIES

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Hierarchical Constrained-Random Test Generation USES Extracted graph relationship

Opcode Generator USES Extracted graph relationship

CITATIONS

6 sources

6 citations — click to expand

[1] Test knobs are knobs or switches that let a test writer generate constrained stimulus and steer a random generator. Generating AMD microcode stimuli using VCS constraint solver

[2] The opcode generator uses a two-layer architecture in which a SystemVerilog random-sequence upper layer uses weighted knobs to control high-level item distribution, while the lower opcode class is randomized with constraints and weights from the upper layer. Generating AMD microcode stimuli using VCS constraint solver

[3] Tests consist of weighted values that direct the generator to a required mix of instructions, and the constraint solver applies those weights to control opcode-type distribution. Generating AMD microcode stimuli using VCS constraint solver

[4] Opcode categories in the multi-class generator were chosen to map well to the knobs or weights used in the test interface. Generating AMD microcode stimuli using VCS constraint solver

[5] In the described architecture, the test layer did not directly constrain subclass items; the upper layer was controlled by knobs only and selected the opcode category first so the correct subclass object could be allocated. Generating AMD microcode stimuli using VCS constraint solver

[6] If tests directly control lower-level items, a wrapper class may be required and randomized before allocating and randomizing the correct subclass object. Generating AMD microcode stimuli using VCS constraint solver