adding immutable testing

immutable-testing/Cargo.toml

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+[package]
+name = "immutable-testing"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

immutable-testing/Makefile

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+format:
+	cargo fmt --quiet
+
+lint:
+	cargo clippy --quiet
+
+test:
+	cargo test --quiet
+
+run:
+	cargo run 
+
+all: format lint test run

immutable-testing/src/lib.rs

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+/* Calculator that uses an immutable vector
+Lets make our vector a constant so that we can use it in our tests
+*/
+
+// a vector of immutable integers
+const V: [i32; 3] = [1, 2, 3];
+
+// add all the elements in the vector
+pub fn add() -> i32 {
+    let mut sum = 0;
+    for i in &V {
+        sum += i;
+    }
+    sum
+}
+
+/*These are the tests */
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_add() {
+        assert_eq!(add(), 6);
+    }
+}

immutable-testing/src/main.rs

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+/*
+Uses lib.rs to add all the elements in the vector
+*/
+use immutable_testing::add;
+
+fn main() {
+    //print the result
+    println!("The sum of the elements in the vector is: {}", add());
+}