Add offchain gas_price test

core/src/env/engine/off_chain/db/chain_spec.rs

@@ -75,6 +75,14 @@ impl ChainSpec {
         self.gas_price.decode().map_err(Into::into)
     }
 
+    /// Set the gas price for the chain.
+    pub fn set_gas_price<T>(&mut self, gas_price: T::Balance)
+    where
+        T: EnvTypes
+    {
+        self.gas_price = OffBalance::new(&gas_price)
+    }
+
     /// Returns the minimum balance for an account on the chain.
     pub fn minimum_balance<T>(&self) -> Result<T::Balance>
     where

core/src/env/engine/off_chain/mod.rs

@@ -254,6 +254,10 @@ impl EnvInstance {
             .last_mut()
             .ok_or_else(|| OffChainError::UninitializedBlocks)
     }
+
+    fn chain_spec_mut(&mut self) -> &mut ChainSpec {
+        &mut self.chain_spec
+    }
 }
 
 impl OnInstance for EnvInstance {

core/src/env/engine/off_chain/test_api.rs

@@ -25,6 +25,7 @@ use super::{
 use crate::env::{
     EnvTypes,
     Result,
+    engine::off_chain::db::ChainSpec,
 };
 use ink_prelude::string::String;
 
@@ -210,6 +211,16 @@ where
     .map_err(Into::into)
 }
 
+/// Update the [ChainSpec](`crate::env::engine::off_chain::db::ChainSpec`) for the test environment
+pub fn update_chain_spec<F>(f: F) -> Result<()>
+where
+    F: FnOnce(&mut ChainSpec) -> ()
+{
+    Ok(<EnvInstance as OnInstance>::on_instance(|instance| {
+        f(instance.chain_spec_mut())
+    }))
+}
+
 /// Returns the contents of the past performed environmental `println` in order.
 pub fn recorded_printlns() -> impl Iterator<Item = String> {
     <EnvInstance as OnInstance>::on_instance(|instance| {

core/src/env/engine/off_chain/tests.rs

@@ -68,3 +68,19 @@ fn key_add_sub() -> Result<()> {
         Ok(())
     })
 }
+
+#[test]
+fn gas_price() -> env::Result<()> {
+    env::test::run_test::<env::DefaultEnvTypes, _>(|_| {
+        let gas_price= 2u32;
+        env::test::update_chain_spec(|chain_spec| {
+            chain_spec.set_gas_price::<env::DefaultEnvTypes>(gas_price.into())
+        })?;
+
+        assert_eq!(2u128, env::gas_price::<env::DefaultEnvTypes>(1).unwrap());
+        assert_eq!(20u128, env::gas_price::<env::DefaultEnvTypes>(10).unwrap());
+        assert_eq!(6u128, env::gas_price::<env::DefaultEnvTypes>(3).unwrap());
+
+        Ok(())
+    })
+}