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+This tool is used to analyze cts reports. Three scripts are included and can be used separately.
+
+# Terminology
+### Report
+A report can be either a standard CTS result zip file, or a test_result.xml file.
+### Information files
+"Information files" indicates three files: `info.json`, `result.csv`, `summary.csv`
+
+# Scripts
+## parse_cts_report.py
+### usage
+```
+./parse_cts_report.py -r REPORT -d OUTPUT_DIR
+```
+
+The `-r` flag must be followed by exactly one report.
+
+The `-d` flag specifies the directory in which the information files will be stored.
+
+## aggregate_cts_reports.py
+### usage
+```
+./aggregate_cts_reports.py -r REPORT [REPORT ...] -d OUTPUT_DIR
+```
+
+The `-r` flag can be followed by one or more reports.
+
+The `-d` flag has the same behavior as `parse_cts_report.py`.
+
+## compare_cts_reports.py
+### usage
+```
+./compare_cts_reports.py [-h] [-r CTS_REPORTS [CTS_REPORTS ...]] [-f CTS_REPORTS] --mode {1,2,n} --output-dir OUTPUT_DIR [--csv CSV] [--output-files]
+```
+
+One `-r` flag is followed by a group of report files that you want to aggregate.
+
+One `-f` flag is followed by **one** path to a folder, which contains parsed information files.
+
+The `-m` flag has to be specified: `1` for one-way mode, `2` for two-way mode, and `n` for n-way mode.
+
+The `-d` flag has to be specified. Behavior same as `parse_cts_report.py`.
+
+`--output-files/-o` is a boolean flag. If users specify this flag, the parsed results of reports after flags `-r` will be outputed into the information files.
+
+`--csv` allows users to specify the file name of the comparison result. The default value is `diff.csv`.
+
+### modes
+#### One-way Comparison
+The two reports from user input are report A and report B, respectively. Be careful that the order matters.
+
+One-way comparison lists the tests that fail in report A and the corresponding results in both reports.
+
+#### Two-way Comparison
+Two-way comparison lists the tests where report A and report B have different results. If a test only exists in one of the reports, the test result of the other report will be indicated as `null`.
+
+#### N-way Comparison
+N-way comparison mode is used to show a summary of several test reports.
+- The summaries are based on each module_name-abi pair. We call this pair "module" to simplify the explanation.
+- Modules are sorted by the lowest pass rate among all reports. That is, if a module has a pass rate of 0.0 in one of the reports, it will be listed on the very top of `diff.csv`.
+
+## Tests
+```
+./test_parse_cts_report.py
+./test_aggregate_cts_reports.py
+./test_compare_cts_reports.py
+```
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