an assay device for testing of liquid samples for drugs of abuse has a transparent container for retaining a liquid sample . a backing member is within the container and is curved so that its front surface corresponds to the curvature of the container wall . immunoassay test strips are on the front face of the backing and are visible through the container wall . each test strip is enclosed in a transparent pocket which has a bottom opening through which the bottom portion of the test strip protrudes to contact the liquid sample within the container . the liquid then flows upwardly through the test strip to react with reagents within the test strip .