The present invention discloses an apparatus and method for minimizing or eliminating steps in immunosorbent assays by eliminating both the need to attach target molecules to the test well and the need to remove unbound antibodies through rinsing. The single-step immunosorbent assay (SISA) includes the step of mixing the immunologic molecules with the sample and detection. SISA is utilized for a single analyte or target. The present invention further discloses a single-step immunosorbent assay for multiple analytes (SISAMA) for testing a plurality of analytes or targets in a single well using a modified SISA test wherein different fluorescent tags are attached to different antibody pairs. The present invention further includes various types of cassettes having test wells for the rapid and simultaneous testing of fluids for a plurality of components. Embodiments of this invention uniquely utilize colorimetric reagent reactions for ease of testing.