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.